Hi - have left our kids with kindercare sitter when staying in Walt Disney World, several times - from the ages of 16 months and 4 years. They were great. If u use them more than once in a trip they try to assign the same sitter.
The ladies who sat for us were all around about late fifties, early sixties and were lovely. They bring a suitcase of toys appropriate for the childrens ages. Months after the trip my two insisted one of their favourite things at WDW was spending the evening with the sitter.
They will also take your children out if you want, tho I don't think I would want to send them with my two until they are a bit older - a bit of a handful at present.
We also used Fairygodmothers when staying off-site and their service was great too but, I just love Kindercare.
I will hunt out the phone number for you and post it later.