I don't know much about Kayaking so I cannot offer too much advise. The one weekend I did use the dive-Kayak combo it was fantastic but I was with people who knew the area and how to set an appropriate anchor. We would die our kayaks together and dive along a wall so that navigation was pretty simple.
The tips I do have, is yes tie your yaks together when you leave them...and while underway do make sure everything is clipped in (mask, fins, etc. I did roll my kayak at one point...) Also Keep some air in your bcd. I was doing this in California, with a 23lb weight belt. we would get our suits on fully while still in the kayak, then weight belt and all additional gear.
Now, getting back in the boat....
I found it was easiest to but the boat between you and your BCD setup, rest with your arms over the boat (and body still in the water), and hoist the gear into the kayak by pulling. It worked a lot better for me than my first attempt of picking up the gear and putting it in the boat while your still in the water.
I had a blast and while I am used to long surface swims, having Kayaks allowed me to go to really wonderful sites, and many in the same day.
Good luck!