Old iPhone for child reset to factory default

I think I messed up. I erased and reset my old iPhone when I got an upgrade so I could give the old phone to my daughter to play with and use for school when she needs it. Is there a way to set it up without a plan? Or do we have to add her to the plan and get her a phone number just to activate the phone? Because my husband won’t do it and I have one disappointed kid.