Hi eyeknee!
We are living in Colombo for 1 month and we have small daughter 2 and half y.o. We have found some playground here. In Cinnamon Grand is a good one in Cheers Pub. There are not many children in the day time but in evening and holiday it can be many. There are TV, games, many toys and good children cuisine. We are often going there.
Another one is in Majestic city. We prefer to go there in the daytime, because in other hours there are too many children.
If you want we can meet somedayand have a nice time. Especially we would be happy to find new friends for our daufhter.