This is a beautiful beach with great views of Molikini and Lanai on clear days. The beach has good swimming for most levels close to shore. The area immediately in front of Makena Surf can get some bigger waves given the pitch of the shore, so little kids do need to be a little careful there.
The snorkeling here is awesome. You can swim in either direction along the rocks and see tons of sea turtles, fish, eels, octopus, etc. There is a solid quarter mile to half mile of coast line on which to snorkel here.
A few words to the wise.
1) There are not that many places to easily climb out, so do not plan on snorkeling one direction and walking back. You will likely need to swim back to your access point.
2) Be careful with wind. Later in the day when the wind blows this can get the current moving here. It won't do anything like tow you out to sea, but the current can make a swim back to your access point a lot longer than the swim out. If it is windy be sure you are cautious about how far you swim away from the beach.