I don't know if you do anything like this on piano, but our piano teacher is big on hand and finger strength. Especially for DS8 because he is really playing songs beyond his hand strength and size. We do Hanon exercises every day for 3-5 minutes and it has made a HUGE difference in DS8's hand and finger strength. And not just in piano, but in general dexterity too(he's not 2E, but has never been a small motor guy. He's a sloppy writer.) Your piano teacher may have suggestions here too.
http://www.amazon.com/Virtuoso-Pianist-60-Exercises-Schirmers/dp/0793525446/ref=cm_cr_pr_product_top
