...they are adorable. But I'm worried that the cage we have for them (smooth walls on bottom floor, then ramp up to barred upper floor) isn't escape proof.
The bars are less than 1cm apart (the blurb said 8mm but it looks more like 9mm when I tried with a ruler) but the mice are 5 weeks old and so teeny...couldn't they squeeze out if they tried? So far, they haven't even shown interest in the bars. Too busy exploring the endless hideaways and toys that dd has crammed in. But I'm nervous.
We could take out the top floor and keep them in just the bottom half, but its half the space. Till they grow. Or wrap masking tape around the bottom 2 inches of bars? Or am I stressing over nothing, the way I did over my girls when they were newborns?! 
Utter mouse novice. Any advice welcome please.