Congratulations! I noticed a similar attitude shift with my son when we pulled him out of school. He gets so much more out of these additional activities now too.

My DS8 isn't a big fan of writing either, but we consistently journal every day, if only for a few minutes. I typically try to pick writing topics he's interested in - the books he's reading, how to play a video game, write a story about a crazed alien taking over our city and then underline all the nouns, etc etc. Typing can help too. Be creative and consistent when you start. But you may want to continue to give him a break until he seems ready.