We travelled as a family to Amalfi last Summer for a wedding. Mom, Dad, a 6-month old and a 2-year old. We were at Marina Riviera for 4 days - from the moment we stepped in the door until we left, we were taken care of, and made to feel at home, every step of the way.
If we're ever in Amalfi again, although a little pricey, we will definitely stay here again. Well worth the extra $$$'s.
We had our 2 children in and out of the pool a fair bit and the water was a touch cold - that was literally the only un-enjoyable part of our stay. That, and outside of the pool, there really wasn't a lot of activities, at the hotel, for kids.