The Club Med is nice but nothing like the JW. They're on opposite sides of the island so you'd need at least 30 minutes to taxi from one to the other. The Marriott property is more about relaxing, the Club Med is more about activity. The Club Med property is surrounded by other hotels, shops and touristic sites, so it will be the lively part of your trip. The JW is more secluded.

As for kids, I can't offer anything specific, but consider hiring a full time nanny to help you out. Check around and you should be able to find plenty of candidates more than happy with $50/day. They might even pick up some Thai!