To add to what Tkaelin said you also have Cobalt Coast a short distance away also a very good shore dive you basically have 4 very good shore dive locations in that area with tank and weight rentals on site ...also gear rental if needed
They offer 2 bedroom suites at Cobalt Coast, see below. They also have some stand-alone cottages but I think that they are 1 bedroom? The shore dive at Cobalt Coast has a tendency to get winded out in winter and that might extend into March, I am not sure.
@Todd C. I see that you are from Colorado so I wanted to mention that Cayman Airways is offering non-stop flights from Denver to GCM, starting in early March, so that would make your journey easy, even if you decide to continue on to LC, see link below:
Welcome to Cayman Airways
You haven't mentioned budget and if that is not a concern then that's great, and you can have your choice of Cayman properties; but taking 4 divers to Cayman and doing exclusively boat dives can get very pricey, especially if you want to do a lot of diving. Shore diving is a good way to cut diving costs on GC and it is very convenient when you are staying at a place that offers an onsite dive op that includes shore diving - like Lighthouse Point, Coconut Bay, and Cobalt Coast.
Feeding a family of 4 is also expensive, on Grand Cayman there are many choices and price ranges for places to eat and well-stocked grocery stores, so a condo that will allow you to prepare some of your meals is a great venue.
Staying at a small, diver-dedicated all-inclusive resort is another good option, especially on the sister islands of Brac and Little Cayman where restaurants and grocery stores are limited, and it can also help to control costs. The Clearly Cayman Resorts including CCGCR, CBBR and LCBR (and The Club at Little Cayman) are popular options.
GC has by far the most topside activities for a family but it is also the most developed destination. The north end of 7MB and the West Bay area north of 7MB are not too far from the popular spots but still quieter and less developed, but you will need to rent a car.
You haven't mentioned if your family likes white sand beachfront accommodations? If they do then a condo on 7MB is a great option but it can get pricey - but there are ranges - and you would have to take your gear to a shore diving site like Turtle Reef if you want to supplement your boat dives with shore dives.
Lots of good choices are available, but again, March is still the high season and Spring Break is a very popular time of year so don't wait too long!
Cobalt Coast 2-Bedroom Suite
- Ocean view rooms with one bedroom with 2 full size beds and ensuite bathroom
- Second bedroom with 1 king or 2 full size beds plus second bathroom with door that opens into bedroom and hallway from lounge
- Lounge area with small refrigerator and full sleeper sofa
- These rooms are a combination of a 1- bedroom suite and a garden view lock- off room
- Room safe