Handwriting without tears is our go-to writing program (if you are talking about the physical act of writing, not the composition aspect). It is multi-sensory, developed by an occupational therapist and used in a lot of schools now.
If I had that kind of money to spend, I would probably do Brainpop, books, art supplies and educational toys & games. A good quality globe and some maps would also be on the list if I didn't already have them.
A good quality chalk or whiteboard might also be a good buy if you don't already have one. A lot of times my child isn't really interested in doing a worksheet type thing or writing out information on paper, but you write the same information on a board and it is suddenly much more interesting.
Mom to 10yo Autistic Wonder Boy and 6yo Inquisitive Fireball Girl . December birthdays.