We (my kids are 18 and 12) did a very similar trip a few weeks ago in December, staying in the adjoining Royal Livingstone. The hotel was fine but I'd probably say the Zambezi Sun is better for families. The whole Royal Livingstone/Zambezi Sun complex seemed a little artificial and "Disneyfied" for us but as a base for a few days it's very convenient for the Falls and you'll be well looked after.
All our accomodation, ground transfer and activity arrangements were booked/arranged through go2africa.com, who used Wild Horizons as their local activity provider. Both their websites would be useful for you.
Depending what other safari-type activity you're doing, we found the Chobe day trip very good and even the journey there and back (across the Zambezi) was interesting.
Have a great time!