I think I understand what you're asking...
You should create a routed link between the sites. This would mean creating a new subnet purely between the switches/routers which link the sites, or use routed ports on your HP switch (whichever is most suitable) with a small /30 subnet.
If you configure IP helpers on each site, they won't really be a problem as the local DHCP server should respond first and offer an IP address. The client should only accept an offer from the remote DHCP server if it doesn't receive one from the local subnet.
You won't need to create Superscopes either, as the DHCP server will know the netmask based on its own NIC.
Also, you'll need to configure some kind of routing between the two site routers, or configure static routes so each LAN knows the way to the other one (vital for DHCP to be able to service hosts on the remote sites).
Hope that makes sense