You can plan a trip to Malaysia / Bali / Hong Kong
Dubai is also a great pick but it will be hot
I have written a detailed blog on my Top international pick for this summers where you can travel with Kids. You may pls read that for more suggestions.
Answering this is little difficult as many theme or water parks have age restrictions. You are a well travelled person, hence you would know how important it is to know age of the child.
Suggesting some family friendly destination for Indians.
1) Malaysia ( KL, Getting , Mallacca, Penang)
2) Mauritius ( opt for good resort, as they have kids play area as well)
3) Dubai ( a mix of night life, water & theme parks & good hotels)
4) Taiwan (national parks & night life)
5) Phillipines ( beaches as well as night life in cities)
6) Hong kong ( Disneyland is the main attraction)
7) Swiss ( good clubs can be found majorly in Zurich & Geneva than in other cities). Also Swiss miniature is worth visiting.