G.D.
Sounds like you have great kids, good job! Too bad you grew up with such resentment/hatred for your brother's piano activities. Perhaps you better understand your parents' and your brother's perspective now that you're in a similar situation. And use your memories about what you did not like, to adjust your own parenting, to make sure each child feels like they are "exceptional".
One thing that struck me was that by having a family meeting about the 11 yr old's "great gift", it's highlighting all the more (to the other kids) that he is more special. Seems like this is a parent decision, not a kid's. They shouldn't be aware of (or at least reminded about) the big discrepancy in funds devoted to each one. Of course their input is important. But if you're asking another child if they "mind" if you redirect family time and money away from them so it can be devoted to another, that's setting them up to feel inferior.
I'd be a little suspicious of the "pay for play" deal and scholarships, and yet you need to make a huge financial commitment? Remember that someone is making money from this, and despite their promises, they may or may not truly have your kid's best interest in mind.
The 17 year old has just one year left with you, I'm assuming, and you want to make sure it's a special time to honor his graduation accomplishments, etc. If the 11 year old is truly that talented, and the offers are legit, then they will also be available a year from now.
Good luck in your decision! Congrats on how you've raised such great kids!