Hi Dean,
We cross alone or in a group, it's only 6minutes. Always safer to have someone with you, in case you break your uni in the middle of the channel like I did recently... (and I was on my own..

)
Beginners catch the ferry and rig over there. It's the return tack that's a bit tricky with sometimes large waves coming from the side.
No windsurfing gear at all at the resort, I guess if you wanted to teach someone you'd have to hire gear and bring it on the ferry (could turn out expensive)
I would rather recommend taking the kids at the anse vata beach in the morning, all rentals have ultra large comfy boards and kids rigs. Aloha windsurfing are quite good at teaching and have a dinghy for safety.
Im' going to ilot maitre there for two nights in a couple of weeks with my GF, can't wait to be in the bungalow over the water, I think the buffet meal is around 60$.