Hi
We went to Sri Lanka with our 18mth old in feb 2012.
We stayed at the Max Wadiya and can't recommend it highly enough.
It's an amazing, magical place and it doesn't get more child friendly.
Feb/March is when the turtles hatch if you can time that right.
I have attached the trip advisor reviews below which are just as enthusiastic.
http://www.tripadvisor.co.uk/Hotel_Revi ... vince.html
Good luck. I am very, very jealous.