Hi there,
Blue Angel offers a regularly scheduled 8 a.m. trip as well as 1 p.m., every day. There is also a boat that goes at 11 a.m. that is a dive/snorkel combo boat. Lots of people do prefer the 8 a.m. trip, but I sometimes wonder if that's habit as much as anything. The light on the wall changes pretty dramatically for the afternoon dives, and for me, a late afternoon trip to Chankanaab is one of my favourite things; soooo much fishy sex going on that is amazing to watch. (Does that make me a voyeur??) Behaviours of many fish/critters is different a.m. vs p.m., so it's something to consider!
Regularly scheduled night dives are 1 tank on Tuesday and Thursday.
Shore diving is always available; as others have mentioned, if you want to shore dive outside of hours when the dive shop is open, let the shop know and they can provide weights. Many people choose to dive in the morning, lunch, then shore dive in the afternoon - best of both worlds.
The shore dive is less "exciting" than the reef, but there is lots to see, particularly if you're patient! There are many different types of juvenile fish, tons of different shrimps, crabs and eels, and loads and loads of tiny things in the bottom. My current preference is to head out a bit farther from shore into about 25 feet into the turtle grass and see what's going on out there. Occasionally we are rewarded with an eagle ray right there, as there are plenty of conchs for them to eat.
To the OP, I'm glad the members of your party who did the refresher found it helpful! We've worked hard at the Scuba School to provide opportunities for divers of all levels to improve their skills and increase their overall comfort in the water. The turtle population doesn't vary much by time of year, but there are sites (like Cedral) where they seem to be more commonly seen. It's always a treat to see a "different turtle" - most of our are hawksbills - and Cedral traditionally is a good place to see a green turtle or sometimes a loggerhead.
I hope that helps.
kari