On the educational needs ~ Gather information on what sorts of options people have seen, and go for those that seem to be the best fit for your child. A grade acceleration might be right for one kid, and not right for another, even with the same levels of IQ and achievement (and IAS score).
On the piano ~ What are your goals for learning? What are your son's? If they are to become a world famous concert pianist, then certainly, you need a great instrument. If they are to be capable on a piano, learn discipline, and learn a new skill, then find something he can practice on, and reevaluate the physical piano in a few years. You should also find a teacher who supports your goals. As a parent, I'm seeking an activity that challenges my child, gives them the skills they need to persist on something difficult, and to introduce musical skills. I've not spent much time with teachers who tell me that my DD needs a $3k flute or that my DS needs a better (half size!) violin. I've selected teachers that instead teach the skills, encourage efforts to be self-directed in their learning, and help my kids love the music on their own terms.
