I'll admit it, I did cringe when I read that. But I don't feel like writing an expose on anything right now, so this'll do:
I personally would -not- house them together for various reasons. If they are young, dumeril's boas are known to occasionally eat reptilian cagemates as juveniles.
As adults, the one tank is not large enough to house them all together anyway, so I would look into various types of plastic caging. They are much lighter and easier to clean than a huge aquarium-style tank, and the front-opening design is great for stacking and makes it easier to get larger animals in and out.
I personally like cypress mulch substrate, especially for animals who use higher than room humidity. I get it from the garden center of Home Depot and bake it before using. I have seen little clear wood lice or something in it before, but nothing that's really visible or harmful to the animals inside.
Where I live it's cheap, $1.50 per 2 cu.ft. But availability does depend on location.
-----
-audri
Webpage/Pics