JohnStacy

Nice! Checks out... (with an extra turnaround)

The whole thing about the video game realbook is that it's a collection of lead sheets, not piano sheet music or some other thing like that.  Just melody and chords. Great for a jam situation.

Which, I do happen to be working on, and am happy that there is this conveniently located thread of suggestions to include that I need to get working on.

Following this thread.

This is more or less a list of "If there was a VG Realbook, it would need these tracks in it."
And since I'm making one of those, this could be useful for that.
Butter Building (Kirby Series)
Lost Woods (Ocarina of Time)
Overworld (Every Super Mario Bros.)
Ending (Super Mario Bros 3)
Chocobo Theme (Final Fantasy)
Slider (Super Mario 64)
Tetris A and B Themes
The Moon (Ducktales)
Fourside (Earthbound)

And I'll stop there for right now.
 

Following this thread.

This is more or less a list of "If there was a VG Realbook, it would need these tracks in it."
And since I'm making one of those, this could be useful for that.
Butter Building (Kirby Series)
Lost Woods (Ocarina of Time)
Overworld (Every Super Mario Bros.)
Ending (Super Mario Bros 3)
Chocobo Theme (Final Fantasy)
Slider (Super Mario 64)
Tetris A and B Themes
The Moon (Ducktales)
Fourside (Earthbound)

And I'll stop there for right now.
 

I'm not a multi instrumentalist anymore.
I used to play actively Horn, Trumpet, Trombone, Bass Trombone, Clarinet, Saxophone, Flute, some piano, Bass, and guitar, although I have performed on virtually every wind instrument at some point or another.
My process went something like this:
Started horn in 6th grade band, was very bored with it because horn players don't play real music until high school.  Since I was bored, I got a trumpet and started learning that.  Stuck with both trumpet and horn for a few years, then I learned trombones.  I kind of took a shortcut, doing the British thing and learning treble clef Bb trombone.  Trumpet and trombone use mostly the same positions/valves, so the learning curve was nonexistent.  Just had to learn where the slide positions were.  Later that turned to treble clef euphonium and tuba, which all use the same fingerings as trumpet.  This whole time, I also cheated and used the same embouchure for all the brass instruments.  I didn't sound like a professional, but I was in high school and sounded good enough on horn which was my primary instrument.  Total time spent learning all the brass instruments?  Not very long.  I never actually practiced euphonium or tuba, I could just pick them up and play them because of how similar they are to the other brasses.
While this was happening, I got a guitar and a keyboard for different Christmases.  This meant I had two guitars now and an electric keyboard.  One of the guitars I already had, it was a family instrument.  So I used the new guitar to actually learn the instrument, and the old guitar I tuned down an octave and played it like a bass.  I learned both at the same time.  The piano I learned to read chord changes, but not actual piano sheet music.  For what I was doing that was perfectly fine, since I played in a Christian praise team that only read chord changes.  That was the extent of those instruments, and I haven't really ever gone back.  I can read guitar and bass music, but never have any times where I actually need to play them anymore, since nobody asks me (there are real guitar and bass players out there).  Piano I occasionally play in jazz combos and at churches, so it's a viable source of playing experience and income.
The woodwinds I learned over the course of years.  I learned saxophone and flute at the same time because of a long story I won't get into here where I couldn't play brass instruments for 6 months.  I borrowed a flute and alto sax and learned those somewhat proficiently, and the rest of the woodwinds were easy enough to learn because the fingerings are similar.  Except oboe and bassoon.  Those instruments make sense in a very different way.  I haven't played the woodwinds in a performance in years.  Again, there are real players of those instruments everywhere.  I did play them a lot while teaching, and that was to model a good sound and technique for the kids.  But if I had to pick up a flute or clarinet for a performance, I am reasonably certain I can still do it, because I've kept fresh on fingerings while composing and teaching and the sound will come back with a little bit of practice.

The whole time I was in college, the horn professor begged me to stop playing the other instruments.  I was playing both trombones in the jazz bands, as well as trumpet for gigs, bassoon and clarinet in the reading band, and horn everywhere else.  Then one lesson at the start of a semester I played really badly on horn (I had just gotten done playing trumpet in the jazz band, and ran down the hall to my horn lesson).  The lesson was over at that point, and in a very nice way I was told, either you can keep playing all the instruments and sucking at your primary, or you can focus your work and actually be a good horn player.  I was threatened to be kicked out of the studio because I was actually getting worse at horn.  I had my own horn, which was bout $10000, and I didn't want to waste all that since I couldn't afford to do anything else, so I stopped doing everything else after that semester.
Tl;Dr
You can be a multi instrumentalist and be good at it.  Part of it is being efficient and practicing solid fundamentals that carry over to other instruments.  You aren't going to have the same problems for all instruments.  If you practice bass, your drumming isn't going to get worse for any other reason than you're not practicing your drumming.  With brass instruments, like in my case, trumpet playing messes with horn playing because of not practicing horn and because of the difference in embouchure. 
You are right though, now is the best time for you to learn these things, since you have time and don't have to worry about money.
But you also have to pace yourself.  You're trying to do too much.  You can't learn all the instruments to the level you want to learn them to at the same time.  You will exhaust yourself.  If you learn a few of them well, with solid fundamentals, then gradually add more to your arsenal, you'll have a much more pleasant experience.

It may be late to get in on this, but could I be listed as a performer for french horn?  I would like to start recording for as many different people as possible.