Welcome to the forum and the lake. One thing that can be tough with kids out on a boat is life preservers.
I have always had kids under 12 in life preservers, and have spent a little extra cash over the last few years to get ones that zip up and tie, and are like what you see a lot of bass fisherman wear (who aren't wearing the inflatable ones that look like suspenders).
I found that my grandchildren were more receptive to wearing that type of life preserver than the old ugly orange uncomfortable but safe ones.
Enjoy the lake, and coming out of your marina and Sanders Bay, just watch out for "The Witches", a large area of shallow water and huge rocks that is really pretty well marked, but still seems to confuse people. It goes from west of Lockes Island (the island to the right as you come out Sanders Bay from the marina to North of Governors Island (the island that is to the left of the bay as you come out.
Take your time, enjoy, and be safe. Once again, welcome.