Default S3 for kids

Hi

I've just upgraded to an S4 and want to have my S3 as a tab for the kids. They currently use it with Zoodles turned on which locks off purchasing and visiting the home page. This works Ok but I'm wondering if there are any other alternatives.
I would still like to use the phone myself sometimes but only via wifi. Ideally having separate logins for each user would be great but I'm not sure if it's possible. The kids play games, watch videos, listen to music. Apps are currently purchased on my Google account. The phone had international i9300 Samsung software and is unrooted.

Any ideas or recommendations?

Matt

sent from my twisted mind using interweb magic