We had the same concerns last year. We stayed at Oceanview in Homer and it turned out to be a great decision. No fireworks noise at all to scare our dog. Oceanview threw a cookout on the 4th for everybody in the park. We had a really wonderful time there for a week. Plenty to do in Homer. Our bear sightseeing trip with Sasquatch Alaska Adventures was a highlight--money well spent!
Someone else can tell you what goes on in Seward over the 4th of July. I can't remember, but it involves throngs of people running down a mountain and throngs of RVers boondocking. LOL