Rack system and humidity

So, I plan on building myself an 8' tall by 31" wide by 18" deep rack. It's going to be able to hold 6 41 QT tubs for breeding pairs of leos/adult ball pythons, 6 32 QT tubs for 500-1500g bp's, 8 or 12 15 QT tubs for 200-500g ball pythons or 2 hatchling leopard geckos or one 15g+ leopard gecko. Lastly as many as I can fit on the rest of the remaining shelves 6 QT tubs for hatchling to 200g balls.

Now, if it was just for leo's, I could bang it out in simple plywood and be done. But the humidity requirements of ball's presents the ultimate challenge to rack builders everywhere. So, my question would be, what finish could I use on the plywood to make it water resistant? I've been looking and I think Thompson's Water Seal would do the trick, but I'm not sure if it's been used safely before.

I just want to get your opinions on what would be safe for the snakes!

I posted a product in a previous thread Kodie that I think would be great for this. No VOCs non toxic and a great sealant... "The most effective solution is to seal all edges with an encapsulating sealer. The best product for this purpose is AFM Hard Seal. Both were specifically designed to seal about 90% of the formaldehyde emissions in the adhesives as well as other volatile organic compounds used in the stains or finishes. You may have to apply two or three coats depending upon the humidity in the air, amount of formaldehyde in the furniture, and your sensitivity. Always use thin coats and let each coat thoroughly dry before applying the next. Once the sealer has fully cured in about a week, you should notice almost no off-gassing. "

So, would you say use this after a water resistant sealer?

You don't need a water resistant sealer if you use this stuff.

So I've decided to go with 2 x 4's for the sides and melamine shelves. Going to run flex watt for it all, on two thermostats. So far with heat (and professional wiring of the flex watt) the heating is going to cost $142 before shipping, the tubs are going to cost $101.60, and the wood I haven't been able to price check yet. But, early calculations add up to about roughly $400. Which, I was hoping wouldnt cost so much but I'll be really happy when it's done.