Grand Cayman has absolutely splendid water activities, great snorkeling and scuba. It is more strongly influenced by the culture of the Caribbean than is Bermuda. In my opinion, Bermuda is a bit more formal than is Grand Cayman and a bit more developed. I recommend you take a look at www.bermudatourism.com for some idea of what you might find there. Both islands offer some excellent restaurants so you should have lots of options in a three day trip.
Either place you go should be great. Have fun!

Bermuda pretty but too far north water too cold

nice for golf sort of a Brit feel.

Of your 2 Grand Cayman better warmer water beaches diving

lots warmer water love that diving especially

in the black coral forest also turtles and rays kids love them

Island pretty but pretty flat.

Happy deciding but Caymans for me.

With a 7-month-old baby, I'd look at the shortest flight, but of course that depends where you're coming from.

We have visited and liked both, and used to go to Grand Cayman all the time when our kids were babies. Both destinations are pricey, but for three days that may not be such a big issue.

We found Grand Cayman a very easy destination with little kids. Seven Mile Beach is gorgeous and typically has calm water - perfect for babies. We rented a villa at VILLAS OF THE GALLEON, so we could have the option of getting some meals on our own. There was a huge American style supermarket across the street ( I think it's still there), so we didn't have to lug much with us.

Our kids really enjoyed visits to The Turtle Farm, and the Botanical Gardens, both of which are an easy day trip.

Have a good time!

I wanted to add that I agree with the poster above who said Bermuda would be too cold right now. In fact, we went at the end of May a few years ago and it was chilly and too cold to get into the water. I think the best time for a visit there is probably later in the season- June -August.

I am sorry I missed the OP saying when she was traveling. I scuba and snorkel in BDA in the summer months; but, agree would not do it in March.

Apologies - I forgot to mention that we are planning on travelling the 1st weekend in June. Would it still be chilly in BDA? The tourism site mentions avg. water temps of 75-80 degrees. Also, we will be travelling from Washington, DC so, flight time is probably not that big of a deal.

June would be very nice in Bermuda. I personally think that Grand Cayman is more family friendly and better for beaches and swimming. Bermuda is hard to get around with kids.

I think cmcfong can answer this better than me, but I think early June weather and water temperature might be iffy in Bermuda. Plus, now that I think about it, I have to agree with the post above. Grand Cayman is probably much easier to get around with a baby, since most of the hotels/condos/shops and supermarket are along West Bay ( beach) road.

Bermuda is gorgeous, but I find it's much easier getting around Caymans with a baby.

Bermuda is rocky, and you have to either rent mopeds or taxi, neither very kid friendly. You need transportation to get to the better restaurants, explore, shop, all the beaches.

Caymans is super kid friendly. Flat dry island, you can rent a car, or even walk around the "hub". Water is usually super calm and their be many other babies to hang with.

In Bermuda there is an excellent system of buses and ferries both of which are child friendly so I would not feel limited to a choice between moped and taxi. A moped would not be a safe option with a baby and taxis are very expensive, but a transportation pass is very reasonable and gives one total access. In the Caymans I have rented cars (not an option in Bermuda) and getting around was a piece of cake.
I am a scuba diver and if I were picking between the two for June travel with a plan to dive it would be Grand Cayman hands down. The water MIGHT be warm enough in Bermuda, in Grand Cayman it will be a sure thing.