H.D.
I am by no means trying to sound ugly here, but I had a simular situation with a friend of mine. She has two girls - 2 and 3. They spent the night with us one time. The two year old woke up; got into EVERYTHING in my house. I was very frustrated that her mom, my friend, did not get up with her. Growing up, my mom woke up when we woke up. She "trained" us that as soon as we get out of bed to come and get her. Yes, kids will be kids and they will play... but it should always be supervised. Just think if they would have pushed a chair up to the cabinet and gotten into a drawer with knives in it. I don't believe in locking up everything; that doesn't teach the children limitations. It only teaches them not to do it at "mommy and daddy's house"... but what about when y'all take vacation or visit the grandparents house? I don't think that they should be disciplined because they are not doing anything "wrong or bad"; in their minds, they want to play... mommy's asleep, so they can be big boys and play by themselves.
My suggestion would be to sit them down and tell them that mommy wants to play with them too and if they come and wake up mommy as soon as they get you up then y'all can have more fun playing together; that way they don't have to get into something that can make mommy upset or worry...