You might be shut out of some of the north GC sites if a storm comes through or even if it's too windy. Maybe for a day or two is all though.
But the west side is always fine. Many of the better dives are there also.
Actually of the 3 good shore dives on the north side, if one is too rough the others are usually good since they're around the point.
Once the whole north side was too rough so they moved the boat south. There's some famous dives there also.Probably in late March?
One small catch - there's almost no beach on Cayman that's a dive site. Seven Mile Beach is a nice stretch of white sand beach and you'll see dive boats out at some of the sites but they're too far out from shore. The north sites are ironshore as are the sites around Georgetown. About the only exception is Smith's Cove, a local beach with a shallow dive. On the east end or farther on the NE side it's all boat diving only.
Curacao diving is almost all on the sheltered west side. It's the place on your list for nice beaches with shore dives - there must be close to 2 dozen with onsite operators and food.Probably 2 dozen more with no facilities.Porto Mari is a double reef dive with a locals beach - it will abe hard to find parking on weekends. Cas Abao is also a nice beach/dive site. There's more listed here with pictures and gps numbers -
Scuba Shore Diving Site Listing for: Curacao, ABC Islands
My group does a lot of dives in a week - there we only did 2 boat dives. At several sites, boats were moored at the ball off the beach so it seemed silly. There's a few good dives where it makes sense - Watamula is one or the Mushroom Forest if that's on your list. We also did Lost Anchor to save from climbing down 3-4 vertical flights of stairs with gear.
Curacao for the most part is low current, pretty benign diving. If you do the few east side dives, those can be rougher. I don't believe anyone does except possibly one of the escorted shore dive operations.
The only thing I know about Coz is you sometimes read about the port being closed in their forum here which means the boats don't go out. IIRC it just happened earlier this week. Cozumel is almost all drift diving also - if that meets the "excess current" limitation.