We visited with our 4 year old, 2 year old, and 4 week old.
We moved a couple of fragile things out-of-reach for the kids. After that, they had a lot of fun running/riding around the yard and playing with the boardgames inside. The beach was quite close, and we went every day with the kids.
The kitchen had plenty of utensils, and plastic/kids plates and bowls, so we were able to prepare all the meals we wanted. Nice dishwasher too.
We visited during a rather warm week in February. The west facing bedrooms got pretty hot. There were some fans but the AC is up the other end of the house, so if you don't like warm nights, something to be aware of.
Overall we had a great time, good value, and would consider staying if we end up visiting Mt Martha again.