Hi S.,
Is there a way you can put a gate up? Perhaps at the top of the stairs or into the kitchen? The child proof gates could keep a child out and if they can climb, try two, one on the bottom and one on the top. Sounds extreme but it's really for their safety as well. Or perhaps, come up with a rule that has big consequences about leaving their room before you wake up....
OK OH MY GOD! I just read "beat their little asses" i am sorry but that made me laugh. Serious or not....funny, funny.
Another word of encouragement, just try to be patient, it's hard and perhaps you can ask for help from someone a family member or friend (dad even) for a few hours of sleep. Sleep is very important for a mom otherwise you just might "beat their little asses"....really, see if you can enlist help to get sleep and perhaps be up before them....