Hi dhgeM,
If you're planning to spend 10-14 days in Belize, why not consider spending some time on the mainland too. There are a ton of fun and exciting things for families to do in San Pedro, but the mainland also has some adventures that kids just adore.
On San Pedro, we have fishing, snorkeling, diving, sailing, windsurfing, kite boarding, hiking, two national parks, one of which is an archaeological site, miles of beaches to roam and so many fun community events. On the mainland, you can visit Maya ruins, explore the jungle, go cave tubing, ziplining and horseback riding. Mixing a trip to Ambergris Caye with a trip to the mainland was certainly my favourite way to enjoy Belize when I was a tourist.