Hi @Ocsic yes, that topology is correct, that will basically build a 5GHz backhaul between the APs. It will be a wireless mesh link between the 5GHz AP ports on each AP, then it sounds like you'll be using the ANT-20 omni antennas on the mesh AP at the remote end to serve clients on 2.4GHz. Just make sure you disable the 2.4GHz radio on the gateway AP, and then you can use those antenna dust/cap covers. Do not run what I call "naked" antenna ports, that it, don't just put the caps on and leave that 2.4GHz radio running.
Other thought: what is your use case, and what's the nature of the remote end? Number of clients, the apps in use, performance demands, etc. Because at 250 feet, you might simply be able to avoid a mesh hop (which roughly cuts your performance in half anyway). You might consider simply having a single wired/gateway MR74 AP at your "home site" and a pair of sector antennas like ANT-27 aimed right at the area where the clients are 250 feet away at the "remote site". I have many customers running that solution and working great, and providing better (and dual-band) coverage at that distance. And if you've got 2 MR74 APs, then you can run them BOTH in that fashion from the home site/building for added coverage or load sharing / client balancing if there's lots of clients.
So that 2nd option avoids having a mesh AP in the first place (my advice is always wired when you can, mesh when you must) so you avoid the performance hit, and you don't need to worry about mounting and powering that mesh AP at the remote site. If this was 1000+ feet away, different story perhaps, but at 250 feet, 1 or 2 gateway mode APs at the home site and some patch or sector antennas would work fine. I have many deployments like that for parking lots and sports fields for example, without using mesh APs.
Hope that helps!