We are going on a cruise in February and I was just reading over everything when I did my online checkin.
We have a dinner reseravation every night at 8:30. But that is just for the "formal" dinning room and 3 of the 7 nights the dress code IS actually FORMAL. So first of all make sure of what the dress code is for that dinning room and unless your kids already have cocktail dresses (or you are going to buy them) you won't eat there those nights anyway.
Most cruise lines have TONS of food options that are included in the packages. But it's more the a la cart places by the pool or in the rec rooms etc. You can always get chicken, pizza, hamburgers etc all over the ship.
Also - if you give your kids a snack at 430 or 5... why can't they eat at 8:30? Do you make them adhere to a strict bedtime schedule even on a cruise on easter break? My 7 my duaghter was flexible enough to eat at 8:30 while we were on vacation, as long as she wasn't being forced to not eat after lunch. If you eat lunch at noon ish and then do 2 small snacks at 2:30 and 5 you should be fine. With an 8:30 dinner reservation, they can be in bed by 10:30 or 11.
Having said that..... I actually prefer an all inclusive resort rather than a cruise. We went to cancun a couple years ago (my daughter was 8). We actually stayed in playa del carmen but one of the days we took a day trip to xcaret. If I went back I would stay there - they have a resort right on the property. it's like sea world, the zoo and a water park all in one. There are TONS of stuff for kids to do. You can usually get really good deals that include airfare and everything on bookit.com.
Have fun!