Hi dberry -Speaking as a non-diving spouse, I figured I would weigh in here: my husband and I are definitely biased in favor of Brac...Grand Cayman definitely offers many, many more choices and is a wonderful place to visit: some of GC can be very busy and touristy but other spots are pretty laid back. Why not do both, if you can? Just a quick hop on Cayman Airways from GC to Brac. Whatever you decide, enjoy!
Just want to jump in to say that I have spoken with several non-diving partners on Cayman Brac that love visiting the island, so the idea of spending a few days on Brac after GC - to see how you like both islands is a great suggestion. Just keep in mind that the wait-to-fly after scuba rule does apply to the flight over to Brac and back, so include that when making travel plans. It would be great if you could do a 10-day trip that will give you a good opportunity to check out both islands. We are both divers but we like to spend 2 weeks, one on GC and one on either Brac or Little Cayman.
There is a very high-end and pricey resort on Brac called Le Soleil d'Or, I don't know what your budget is, but if you want to treat yourself to a few days of luxury - that looks like a good place for it!
We usually stay at the much more modest Cayman Brac Beach Resort. It's small, nice, clean and comfortable and they have some nice non-diving options. Free use of the bicycles, tennis court, small gym, free lending library, gorgeous infinity pool, free guest computer off the lobby, and the dining is buffet but consistently very good.
And they have a small spa onsite and the prices are quite reasonable. There is only one woman working there (she does it all!) but I always get a massage while I am there and it is a pleasant experience.
There are shaded hammocks on the beach but the ocean swimming is not good from the resort property, lots of turtle grass, rocks, and the boat traffic. And the TV reception is terrible at the resort (except in the bar) but we've always gotten good Wi-Fi everywhere on the property.
Every night at the resort they offer some activity around the bar like Trivia and Bingo night is a very popular event with guests, locals, and staff all joining in. On Friday night they have a barbecue around the pool that is excellent.
There is a beautiful nature preserve right across from the resort with tables and lookouts and there are many natural beauties on the island. The small Brac museum is certainly worth a visit, and you won't forget visiting Rebecca's Cave.
Others here on SB have said that there is good shore diving and snorkeling available on Brac and that you can rent tanks and weights from both of the dive shops. We enjoy the boat dives and valet services offered by Reef Divers, the onsite dive op at CBBR, but the Brac Scuba Shack also has a very good reputation.