Yes, you can use DDP there. However, you can't order from the individual sushi menu and pay with DDP. You can get sushi as part of a platter on the regular menu.
Never eaten there, so I don't know if it is good or if it is kid-friendly. I do know that restaurant and Teppan Edo serve kids' meals in a bullet train plate that looks rather like a WDW monorail.
Yes it's on the dining plan. The food is good, not great but it's definitely a good meal. The service is great, and I see no reason that it wouldn't be good for kids.
My husband and I ate there for our anniversary and it was wonderful. My hubby loves sushi and although he couldn't order the sushi "a la carte" They had 2 or 3 entrees that included sushi. (we were on the ddp) They also made us an origami heart that said love in Japanese. I my oppinion it is less of a kids place, I think Teppan Edo would be more kid oriented. We did see kids there and it is WDW! Maybe an earlier ADR would have more children in the restaurant than a later one.
1) Sushi, as part of a meal, can be done DDP.
2) Sushi, by itself, cannot be DDP.
3) I would not consider this as overly kid-friendly (even with a kid's menu).