You're lucky if you only have 2. My first litter, every one of them would escape. It started with Heart and Rio, they would be out of the whelping box even though their eyes weren't open. After their eyes were open it didn't take too long for them to get over the short barrier we had so Rally could easily get to them. We then went to a baby gate, they were over that by 5 weeks. We switched to a plywood barrier so they wouldn't have foothold. So they would be in an ex-pen in the puppy room and have the second barrier across the doorway and by 8 weeks we would every couple of days find an escapee. Granted the barrier had to be low enough that Rally could get in because she absolutely hated not being able to check on them.
Even now when I go to a lure trial people call Rio, Popcorn, because if I open the top of the ex-pen she leaps into my arms.