We are looking at the same type of setup for June/July. We did Bora Bora when our twins were eight months and that worked out pretty well with a beachside villa. Downside was that their kids club was 4 years and above and the babysitting service was expensive due to staff needing to take a boat in from the main island. We did Mexico just prior to Chirstmas at the Andaz Maykoba in the Riviera Maya. Their kids club for under 4 was around $10 an hour per child (free above 4 years) and you could do two blocks of three hours. Their baby sitting service that came to your room was about $20/hr for one child and $30/hr for two, which seemed more affordable than other resorts.

I don't know how bad Bali is right now with tourism after opening up after the holidays. We likely would want to wait until the kids are older as we've gone a few times and not exactly a place we'd want to travel to if we were going to spend a lot of time at the hotel. South Africa is going to have colder water than California, it's also winter there in July. The same with Southern South America. We did take our twins to Lima after Mexico and the water there was just starting to get warmer, but no warmer than California in the summer. It was a great destination for going out to eat with the kids. We may take a look at Fiji as well, but we're looking to burn some Bonvoy/Hyatt points and not the best selection of hotels. Though, it would be easy to tack on New Zealand. Japan would be great, but the availability with ANA has not been as good since the country opened back up. We are a bit hesitant to take extremely long haul flights to Asia with lap infants.

Since you are traveling in a larger group I'd likely not go way too far maybe these would be of interest:

• Moorea or some of the other islands in French Polynesia. Nicer resorts will have a kids club. Smaller islands may have babysitting.
• Costa Rica, Andaz looks decent but lacks the clear water. Corn Islands in Nicaragua has everything you are looking for, but likely too difficult to get to with a 1 year old.
• Multiple Caribbean islands will have the beach you are looking for. Not sure which are likely to have the best kids clubs and babysitters, likely Bahamas.