OK, thanks again for the information. I'm a bit confused when you say that one of the Macs is connected as a "guest". Since the Time Capsule has the ability to provide both a "main" and "guest" network, in order for your Mac(s) to back up, they must be connected to the "main" or private network.
As soon as you can confirm things, we will get the first Mac backing up to the Time Capsule. You would want to locate the Mac close to the Time Capsule for the first "master" backup to speed the process. Once you have the first backup done, then you move the Mac around normally since the hourly backups will only take a few minutes.
When the first Mac has completed its first "master" backup, then you can start the backup for the second Mac, which should also be close to the Time Capsule for this process.
I'm not sure about the info above to have AirPort Utility open. This is not needed. We'll provide the instructions for you when you are ready.