I've done many of this sort of trip and enjoy both boat and shore diving. IMO Little Cayman Beach Resort, Southern Cross and Brac Beach resort will meet almost all of your needs. In my experience, their AI and 3 boat dives per day schedules more than make up for not having house reefs for shore diving. No thinking or effort required, You just need to get up in the morning and put one foot in front of the other. At any of these 3 resorts, the boat tends to come back to the dock before 4 pm allowing plenty of relaxation time for pool, bar, a walk or bike ride, shower and dinner at 7ish. If you want even more diving, all 3 offer night dives a few times per week as well.
I've dived Grand, Little Cayman, Bonaire, Curacao and The Brac many times and given the choice, much prefer a week at Brac or LC. I agree a house reef is nice to have but I much prefer having the opportunity to get on a boat and dive Bloody Bay Wall instead.
The quality of wall diving and valet service at Little Cayman and Brac, more than compensates for the lack of house reefs. The choice all comes down to your price point and preferences.