Take him sometime. It's magical in the fall, but can also be quite good during spring migration. If you go in the spring, try to time it with the full moon and Red Knot migration/Atlantic Horseshoe Crab egg laying. It's quite the spectacle!
If you go in the fall, anytime is great birding, depending on what species you're targeting. First 2-3 weeks in October is gangbusters for hawk migration, plus a good all around time for passerines and monarch butterfly migration as well. Make sure to check out CMBO (Cape May Bird Observatory) and their schedule. Your son may be able to go on a photography walk with some of the greats, like Kevin Karlson or Scott Whittle.
I sure do miss the place and haven't been in about 8 years.