Here's what I would do:
1) I wouldn't really worry about two separate fermenters. I would just use a 6.5 gallon carboy or one of the 7.9 gallon buckets. Just rig up a blow off tube using the main body of a three-piece air-lock, a 1/2" hose, and a jug half filled with water or sanitizer. This way you don't have to worry about getting the additives split up exactly equally. If you absolutely have to use two fermenters, I would still mix it up in one and then split it equally into two carboys so you know everythings is homogenous.
2) I haven't made one of the brewhouse kits, but I imagine the big differences will be fermentation temps and times.
-Ideally, for a lager you want your wort to be at least at fermentation temps before you pitch your yeast. I've also heard to pitch with the wort a few degrees cooler than ferment temps and let it rise naturally to your ferment temps. If you pitch at room temp the yeat will create a lot of esters and/or phenolics you don't want in a clean lager. They can also produce fusel alcohols
Also, with a lager, you should really be sure to pitch plenty of yeast. That activator pack will not be enough on it's own. You can either purchase multiple pack of the yeast or you can make an appropriate sized starter. Check out
www.mrmalty.com for info on how to make a yeast starter and for a pitching rate calculator.
The lagering phase doesn't actually technically start until after fermentation. Your going to ferment to completion in your primary, then rack of the yeastto a secondary and drop the temps much closer to freezing. That is the lagering (cold conditioning) phase.
Also, your never going to get a beer down to a SG of 0.994. In beer you're going to always have some unfermentable sugars. I would guess a mexican style cervesa will have a target final gravity of around 1.008-1.010.
All of that to say, with this being your first beer, a lager may not be the best way to start out. There's a lot more involved than there is with an ale. My sigguestion would be to just follow the instructions for now, and then after a few ales when you're nice and comfortable with brewing, you can move to lagers. You can still use that chest freezer though. Use aclean american ale yeast like Wyeast's 1056 or White Labs WLP001 and ferment it somewhere around 62 degrees or so and you should end up with a very nice clean tasting ale. No, it won't be a lager, but I bet it will still be very nice!
If you do go the route of an ale, I would even suggest not doing a secondary. Most experienced homebrewers have given up doing secondaries on ales unless you're dry-hopping or using fruit or wood. Just let it ferment out and sit for a couple weeks or so to let the yeast clean up after itself.