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I think you've covered the points with the dive kit. Similarly the suggestion here have been sensible.
Eat something before you leave like porridge, that has a slow release of energy, that will help to keep you warm during the dive.
Use the toilet facilities before kitting up!
Use a windproof to keep the wind off before the dive, and after. Even though you are in a drysuit, the action of evaporation of water off the drysuit surface will cool you. If you are shore diving, you have the opportunity to remove the suit between dives, which is a sensible option - and gives you the opportunity of another toilet break before kitting up for dive two.
Warm drink post dive and fast energy food is a good idea too.
If you are getting cold get out before you get really cold. If you get really cold it can take a long time to warm up. If you do get really cold, think seriously about skipping the second dive.
If your hands are cold get out before you lose dexterity - and get thicker gloves, mitts or dry gloves.
On the subject of gloves and hood. If you are using thicker gloves and hood, you will lose dexterity. This makes all the skills you can normally do a little bit harder. Lifting a mask to clear it, feeling for loose hair, repositioning a mask, etc. A lot of cold water divers have the hood fitting close to or over the mask skirt. Again, until you are used to it, it makes mask clearing harder. Mitts make life more interesting, as do dry gloves.
My normal recommendation is to practice in the pool with the hood and gloves until your are comfortable and confident - rather than suffer in the cold water.
Students often cut the hood back to avoid the mask, making mask clearing easier, which is OK, but you are removing protection from your face.
Someone commented about the water on your face. If you have the opportunity before you submerge, rinse your face in the water. (Even if its only breaking the mask seal and filling the mask up). As previously stated, if the waters near freezing its like a sucker punch if you aren't used to it. If you are doing mask clearing exercises, do a partial flood to let your face acclimatise. Don't be surprised if your reaction is a sharp intake of breath, that you are reluctant to release - remember to 'try' to breath normally. Once you are used to it its no real problem.
Don't over purge regulators if the water is really cold (SMB's). Filling SMB's with savage purging is a good way to start a freeflow.
On the subject - if you start getting air dribbling out of your regulator or your AAS (assuming your AAS is on the same first stage) - its a potential warning that you may be icing up - as is ice hitting the back of your throat
If you do have a pony cylinder - get used to using it. i.e. its physical position and the weight shift. It can effect trim. Some people put weight on the opposite side to compensate for the effect on trim. i.e move the weight around.
Probably not on this trip, unless you are really comfortable. But get used to doing regulator switches to the pony cylinder. So it is a familiar, easy and comfortable skill. You don't want to do this the first time in anger!
Pony cylinders should be ON. And FULL. And not used to extend dive time. They are not decompression gas cylinders, and not part of the air calculation for the dive. They are there for backup in case of a failure of the primary.
For reference - do some air calculations for how long it will last at different depths. Do the calculations with double or triple your normal breathing rate. If you have to bailout to the pony your breathing rate will be elevate, at least until you reach a personal perceived point of safety. (When they forced failures on Navy divers, for most, their breathing rate was triple or higher than their normal breathing rate until they reached the first decompression stop - which was their perceived point of safety and control.)
Above all enjoy the experience.
Gareth
ON and FULL makes sense to me. Why have it if you don't? It's emergency backup. Probably needs a longer hose on the second stage. I might as well dive with it this weekend, as I'll be hauling it with me. I'll practice deploying it.
I'll admit to being one of those. I almost answered your title by "but aren't you already diving cold", until I saw what you wrote and understood why you asked 
Now, it's time I start packing for my Thailand trip
(sorry for the unhelpful post...)
I've got short hair and I must be crazy, but I go out the door with wet hair most mornings, even in the dead of winter. Added towel to packing list, since I'd forgotten that! My pile of dive gear in the living room keeps growing. DS undies are a big part of it, LOL! Forgot to add my extra neck and wrist seals to save a dive kit...
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