First I want to wish you and your family, a wonderful, magical first trip as DVC members! You will love BWV, it is an incredible resort.
BWV is a great place to watch Illumination fireworks and on the 4th of July the parks have extra fireworks, so the display is even nicer. It is a very nice display and a great location to see and hear the music. However, the park that really goes all out for the 4th of July is MK. They have fireworks shot off 360 degrees around MK--it is really something to see. MK is always packed on the 4th, but if you go in with this in mind and just go with the flow, it can be a lot of fun. But if you decide to stay at BWV for the 4th, you will still have a great fireworks display.
The CH also has some holiday related crafts for the kids, pool games going on and one year there was a barbeque at the quiet pool.
Have a great trip!!
I go every year on the 4th, and it's wonderful! One caution, though: if you leave the resort on the 4th, you will take hours to get back! Last year it was bumper to bumper traffic to get back from the MK, stop and go all the way. I have NEVER seen traffic so bad!