My wife and I stayed with her sister's family, a total of 4 adults and 3 children, ranging from 1 to 7 years old. Between the two living spaces, we were able to barricade the younger children and give them enough space to crawl around without getting into anything.
The ground floor has a split level, you'll want a pack and play or something to make sure the crawling kids don't hurt themselves.
The house was great! The kitchen was stocked with all the essentials to cook and prepare our meals. You cannot beat the location - it's a 5 minute walk to the beach. The yard is a good size, and the outdoor shower is perfect for cleaning up after hitting the beach.