Multiple wireless access points and channels

I have a wireless network setup as follows,

1 x Access point, broadcasting SSID #1
1 x Repeater, repeating SSID #1
1 x Access point, broadcasting SSID #2
3 x Repeater, repeating SSID #2

My question is, should they all be broadcasting on the same channel or should the channels be spread?

The Engenius ECB3500's that I'm using have the option to set the channel to Auto, or you can set each one manually. Presumably all the hardware on the same SSID should be on the same channel, but different SSID's should be on different channels to prevent interference.

Any tips on how to optimise this setup?

 

the repeaters should be on the same channel as the master units as all they do is extend range. However, the two master units should be on separate channels, preferably far apart but do a channel scan to see where there is space in your area. Try and keep at least three channels away from any occupied channel.