I've never been, but I don't think it's a bad choice. I think it's pretty good themeing, beach party, clam bake, you know. If I hadn't been insistent on barbecue for July 4 (WCC), it's one of the places we might have gone to instead.
Go ahead and book CMC, but keep trying for Ohanas when you get there, even until the last minute, as they might get a cancellation. CMC is great though, but I think I'd rather be close to the fireworks too.
Cape May is a great choice, and if you time it right you'll be able to see much of the fireworks from the Special Illuminations show, from the bridge, or from the dock area of the BC. You can go into EPCOT via the IG, of course and see all of it, if you wish. It's all a matter of personal taste, but I'd never trade the opportunity to dine at Cape May for 'Ohana. Just no comparison.