August is not a great time (sweltering), but St. John is a great choice. The area in the Southeast that has no road access is fantastic for snorkeling. Hike or bike to those beaches and you're right by the reef.
Pretty much none of the uncrowded islands (ie not PR, DR, Bahamas, Caymans) have varied flight time choices. It's early afternoon in, late afternoon out, airport more or less closed the rest of the day.
I'm trying to think of where your photog skills could be put to use, but nothing impressive comes to mind. Oh, you'll find the occasional scenery or culture shot but you can probably leave your really good camera behind.
I think it's a good choice and I'm not going to recommend other islands. The USVI are a great gateway to the Caribbean. Once you've been there you'll have a sense for what parts are attractive and you can pick a different island off those criteria (eg privacy, culture, beaches, snorkeling, serene beauty, no distractions, vs organized activities, water sports, exploring) that stands out for those qualities. Of course you might hate it all and yearn for activity packed Hawaii