I hope you have a nice cabin, because there won't be much for you to do on sea days. With two small children, there isn't anywhere to go. The pools are salt water and not meant for children, and on our cruise (Horizon) it was always windy on the upper decks. Hopefully, they have fixed this problem on your ship, it's newer.
The activities were not geared to families, in fact, you couldn't have kids in the areas where the activities were. My daughter was bored silly with their kids program. Facilities for kids on the Horizon were the size of two cabins, they just moved the kids around the ship. I tried to take her to a couple of things (she was 12 at the time), one was an art project. She's very good at art. They asked us to leave. She spent a lot of time in the cabin watching cartoons when we weren't in a port.
The hours for the kids program are intermittent. A couple of hours in the morning, a couple in the afternoon, then during dinner. It's over at 10 pm. You can take your children to a smoky bar until 11 pm if you like. As another poster said, the entertainment was painfully bad. But the food was good, and always available. Really, Celebrity is not geared to families, it's geared entirely to older couples. It was cheap but sorry, we just didn't enjoy it.