It all depends on the children you are taking. Young children won't be that thrilled with the ruins.
We were just there, last week, and I was personally appalled at the behaviour of some children on our excursion! The ruins were clearly marked NO CLIMBING and the kids were climbing all over them, we even saw children poking an injured iguana with a stick, sadly the parents did not intercede! The children were so rowdy that we couldn't hear our guide speaking at times.
I know I may get flamed here and if so, that is fine, but in my opinion, parents should be mindful of what their children can respectfully tolerate, ex: long walks, talks that they may find boring etc. when planning excursions. Any persons, young or old that participate in the ruins excursions should be mindful of where they are and treat the area with respect. Before anyone asks, I am a parent and a VERY tolerant grandparent and I would hesitate to take my grandchildren to the ruins because they are young and they'd rather be at the beach. That said, if I took them to the ruins, they WOULD respect the area, the wildlife and the culture, without exception!