D-Link DIR-615 :: Setup Two Wireless Networks On One Comcast Cable Modem?

We have kids in the house and I'd like to limit their internet access to certain times of the day but because of the great amount of devices they use (phones, tablets, laptops, etc.) the only way I could think of doing that easily was to set up two wireless networks: one that the adults could use 24/7 and the other that the kids could access during certain set hours.

Here's the equipment I'm working with:

DLink DIR 615 wireless router
DLink DIR 515 wireless router
Motorola Surfboard cable modem S85101U

I plugged the DLink 615 in, set it up for DHCP client and plugged it into the cable modem. I lef the default 192.168.0.1 IP address for the device. On that router, I also reserved the 192.168.0.199 IP address and assigned it to the DLink 515.I also gave the DLink 515 device the IP 192.168.1.1 so I could administer it.I set the DLink 515 to static IP and made the IP 192.168.0.199 and the default gateway 192.168.0.1.I plugged the DLink 515 into one of the LAN ports in the DLink 615.I set a schedule on the DLink 615 to shut down internet access to the DLink 515 at a certain hour and turn it back on at another time.Everything seems to work ok, but at least once a day we have to unplug and plug the routers to reset them.