Here's some info about Serenade and cruising her with children. I couldn't find much before I went. We are 2 adults and one 9 year old boy. So, in no particular order:
I bought the soda cup and bottled water package. Total waste of money, iced water is available in the windjammer all day. Also, hidden away in the park cafe is a drinks dispenser with sugar free lemonade, mango water, strawberry water, all served free and chilled all day. Children aren't allowed to take their soda cup to the kids club so it's a waste of money.
Ice cream is free in the windjammer all day too.
The kids club is fantastic, best yet. It closes an hour for lunch and dinner but on port days it's open all day and you can go ashore and leave your child onboard and they will be entertained and fed. If you don't fancy a cultural tour with overheating toddler this could be the answer. The staff are really enthusiastic, the range of activities will keep any child happy, and they give out loads of medals, certificates etc which kids love. My son usually hates kids clubs, but he loved this one. Make sure to go on the last night, they make pillowcases which make a fab memento.
Every day there is a family activity like scrapbooking, penalty shoot out, basketball, bingo. We took our son to a lot of activities outside the club - quizzes, mini golf tournament, killer pool, table tennis tournament, card making etc. All the materials you need are free of charge. Nobody bothers that they are at an 'adults' activity.
The Wii is available all day in the crown and castle pub if your child is missing gaming, although they do have these in the kids club but don't let the kids spend too long on them. There is a games arcade which we managed to avoid until the end as its overpriced. The rock climbing is fun and they provide shoes so don't pack those heavy trainers!
My only gripes with the ship are the same as with other cruise lines. Forget about getting near the pool, which is tiny and cold, you need a balcony stateroom if you want anywhere to sit outside. The theatre is always full and sometimes the first show doesn't start until 9pm. The centrum is way too small a place for a dance party, the outdoor 'Arabian white night' was much better.
Finally, being British and accustomed to our non smoking policy I found the smoking really invasive. Some of the lounges stank of smoke, the casino was a no go area for me because of this. The policy is that guests may smoke outside on one side of the ship only, but in reality people were smoking everywhere on deck which I found horrible and certainly didn't want my son to be near.
Overall a fantastic cruise, I wouldn't cruise RCI again because of there smoking policy but I didn't let it ruin our trip.