I agree that an inboard will allow your family to enjoy watersports to a much greater degree than an I/O. However, I believe that a V-drive will better suit your needs.

Why?

1) doesn't sound like you're a die-hard slalom guy anymore and that slalom isn't the sole focus for the boat.
2) V-drives offer more interior room - kids will soon ask for friends to come along. 2 families of 4 in a DD is crowded.
3) while you can certainly wakeboard, surf, tube behind a DD it's easier, IMO, to set up a V-drive for those activities

Good luck with the search!