Child hitting

Ive done home daycare since my LO was 3 months old, now she's 15 months. She's never had a restricted area like the rest of the kids, she basically was free range. Now that she is getting older I'm trying to keep her inside the gate where the kids play. She does ok once in awhile,  but when she wants out she excepts me to get her out. She also is into hitting! Major hitting! She will take a toy and hit all the kids over the heads with them. Anyone have any ideas how to discipline her. I make sure to always tell every kid that hits "we don't hit". I've tried putting her in her crib, but also don't want her to feel her crib is a place she goes when she has done something wrong.. I do timeouts for other kids, but she doesn't stay in the designated area.