You don't have to work anymore. You won the game. You don't have to play anymore. Or, you can play the unstructured bonus content.
I never got the appeal of open-world sandbox type games either.
If I had what you had, I would just:
1) raise my kid
2) build stuff
3) write fiction
4) consume without guilt (media, restaurants, hobbies and gadgets, etc)
I think in any rate there's something to be said for just taking a proper break for an entire year if needed. Why not take a year to just focus on raising the kids, sleeping in if you can, taking it slow and easy. The energy should come back if you give yourself time.
I also agree that lifting weights is a very good idea, but don't stop seeing your therapist.
I never got the appeal of open-world sandbox type games either.
If I had what you had, I would just: 1) raise my kid 2) build stuff 3) write fiction 4) consume without guilt (media, restaurants, hobbies and gadgets, etc)