I ask for work and home emails, as well as home, work, and cell phone numbers.
I would give until Friday, then that's it. If they're really keen to sign on, they would have brought you the deposit.

I usually send out a reminder email along the lines of:
"I thank you for choosing my home daycare. I remind you that to secure your child's spot in my daycare, that I will need the forms and deposit in my hands by date, time. If not, I will continue with interviews. Thank you, and have a nice day."

Good luck!