We're at the MO Library just now with our two kids. There are quite some kids here in the age group the OP has mentioned - I've counted at least six.

The kids club is for smaller children up to about Kindergarden only. And it's not supervised - unless one hires a babysitter for 300 THB per hour. There are, however, two or three activities for older kids a day as can be seen on the hotel home page.

I think that Colonial Suites are better for families as they are within walking distance of the pool, restaurants, lobby etc. Villa guests will need a shuttle to almost any place which is fine if you want to relax in your room but maybe not if you're in and out all the time.