DHCP Releay over IPSec VPN connection

Hello,

we have Netgear FVS routers (336Gv2, 318N, SRXN3205) where we have an IPSec VPN Connection to our Headquater (the Endpoint here is a Cisco ASA). The different Netgeare routers are Small Offices, that are connecte via IPSec VPN to the Headquaters Endpoint. To work behind the Netgear routers, they are configured as DHCP Server, so all the clients at the Netgare router get their IP addresses from it.
Our Headquater has an own DHCP Server. Now we tried to get IP addresses from the Headquaters DHCP Server where we change the DHCP mode at one Netgear router to use it as "DHCP Relay". We entered then the IP address of the Headquaters DHCP Server at the DHCP Relay option of the Netgear router, but after that we didn't get an IP address of the Headquaters DHCP Server to the clients. Isn't it possible to get those IP addresses through the tunnel? Or did we configre it wrong?
We have an IPSec VPN router from another manufacturer, where it's working well through  the tunnel. So I assume, I did no configuration mistake. I needn't to change anything at the client(s) to get the IP address from the Headquaters DHCP Server. 

General background. We want to set DHCP Options (66 and 67) to install new clients. The Netgear router doesn't have the possibillity to set DHCP Options. So we had the idea to use DHCP relay and get the IP address and DHCP Options 66,67 from the Headquaters DHCP Server.

Any ideas?