If your mice can fit in the box, and there is likely no chance for them to get stuck, then go right ahead. It should be okay! If you notice any change in diet, feces, etc. of course, take it out.
Hope this helps!!
-PawPrintPug
Eden :-)
Ming (pug) 13 years
Mei-Mei (pug) 4 years
Teagan (Gerbil) 2 months old