So I made a deal with my daughter 🤦‍♀️

We have a mouse in the house... Don't ask why or how, because I don't even remember. I told my daughter she caught the mouse alive she could keep it... She hasn't yet, however my resourceful 12 year has come up with a trap, and now I'm pretty sure it will work. In fact she called me to her room to show me evidence of it working, but she yelped and scared him away. I was taking a snap chat, and as I was leaving in fact recorded him leaving her room. Anyhow, I have a 20 or 30 gallon tank I had plan on putting a small lizard in for myself, but I'm not breaking my promise. what's the best way to convert this into something nice for the mouse. If she actually catches I will indeed tell her she will probably never be able to hold it

TLDR daughter is trying to catch a mouse alive, how do I make a 20-30 gallon tank into something decent for it to live in