In this scenario I typically set up a IPSec tunnel between the ASAs and then set up the GRE between the 2 routers that sit behind the ASAs.
In other words, create your 2 IP addresses that will be used as the GRE endpoints. Permit those in your IPSec tunnel between your ASAs. Make sure each ASA has a route to its respective router’s GRE endpoint. Make sure each router has a route pointing to the ASA for the opposite GRE endpoint. At this point your tunnel should come up and you should be able to add the tunnel addressing to EIGRP as normal.
I’ve done this TONS of times and never had any problem with it so I think you’ll not have any problem.
If you need any more detailed help just ask.