Two Inter-Connected Routers, Two WAN Connections, One DHCP Server?

I recently bought the EA6500 Linksys router and thought I'd replace my old DIR-825. I was using the old one as an occasional go-to for WAN PPTP when US VPN was needed and it was then sent to all devices on the network thanks to DD-WRT. When no longer needed, switched settings back to Automatic Configuration - DHCP. Now, when I try to do it on the new Linksys (DD-WRT not available), there's not enough settings to authenticate. Whatever, don't wanna slow the new one down anyway. So, I connected the old router's WAN port to one of the new one's clients. On the old one, left the same PPTP settings as before, just changed the old one's IP address to 192.168.1.2 and the DHCP pool to starting from 192.168.1.200 (so the two routers don't interfere). Now, I have what I expected. It works amazingly. Let's go a little higher.

I've got two DHCP servers now. Linksys(new) is working with 192.168.1.1, D-Link(old) is working with 192.168.1.2. (Let's not forget D-Link's WAN connection depends on Linksys's internet connection to connect to PPTP). Now, I looked for questions about using ONE DHCP server for these two routers, and got answers for bridging, and stuff. After skipping all those, found some about DHCP Forwarder. Looked liked the right one, but unfortunately was for bridging or using the second one as a router, not a gateway (IF I understood correctly). I even saw things like RIP, RIP2, etc. But didn't wanna start studying those in case they were really not what I was looking for again. (Firewalls are disabled, and NAT and QoS are on, if anything.)
So, final question, how would I use my two routers(or two gateways), where one connects to the internet using the other's, with only one DHCP server so I can still access the devices connected to the second router when I'm connected to the first one? If this is impossible, workarounds, maybe?
Thanks a bunch!