Should be fine. Preferably they should use different channels on the APs that are near each other.
Note that in the 2.4GHz space "different" means ideally 5 channels apart. The channels commonly used for this reason are 1,6 and 11. Also if it's not possible to have adjacent APs use different channels, then have them use the same channel. Refer to the image below.
Let's have an example. Let's say we have two APs that are in the same area:
- Ideally they should be using different channels e.g. 1 and 6 or 1 and 11, or 6 and 11.
- If that's not possible, have both on the same channel.
- Don't put them in for example 1 and 2. While 2 is technically a different channel it interferes a lot with 1. And to make matters worse, the devices using airtime will not respect each other's CSMA/CA messages as they are on different channels. So this is the worst situation you can have.
No need to worry about this in 5GHz, which is one of the reasons why 5GHz is preferred.
And as @kYutobi mentioned, make sure Air Marshal doesn't block the other SSID.