I have an empty 55 gallon tank I want to set up for crested geckos. I know a lot of people keep pairs or trios in 29 gallon tanks, so would four to six females work in a tank this size?

This is what I have so far:
tank
stand
130w PC lighting system with moon lights (bought it for aquatic plants when I had fish, but I'd like to put it on the tank with the cresties unless it'd be harmful for them.) Here's a link to the light: http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=11418&N=2004+113345
60# of small natural-colored gravel
rocks I used in the aquarium that I can boil and/or bake if that will make them safe for the cresties
clean driftwood I never got around to putting in the fish tank

Here's what I'm thinking:
First a layer of gravel for water drainage, then about 4" - 6+" of sterile potting soil (I don't know what brand is good for herps). How much would you reccomend? I'm not sure if I should put the plants in pots in the soil or not. Pros? Cons? I'm sure it'll take a while for the plants to grow large enough to hold the weight of the geckos, so I'll buy more branchy pieces of wood.

Are there species of plants that stay small enough to live in the tank (with regular pruning, of course) that will support the geckos? If there aren't, I'll just leave the driftwood in the tank for them to climb on. (In case it isn't obvious, I'll be making sure that any plants I put in the tank are safe for the geckos.)

I'd like to buy a glass cover for the tank instead of a wire mesh one to help with the humidity, but I don't know how they'd get air if it's tight-fitting. I can't put holes in glass, right? Are plexiglass hoods available somewhere? What would work?

I'm thinking of using one of the humidifying thingies I found at Petco in the tank: http://www.petco.com/Shop/Product.aspx?R=3241&Nav=1&N=0&Ntt=humidity&cp=2&Nao=12&sku=843210&familyID=10190& Would this be a good idea?

Would this work? What should I change? Any suggestions for other things I should add? I'm sure I've missed at least a few things. =)
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Cake or death?