I would start from this post by pcunite (the same author of the main VLAN related tutorial on the forum: http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1 ):
http://forum.mikrotik.com/t/guest-vlan-with-router-ap-using-new-bridge-vlan-filtering-sample-config/124903/1
It seems like your setup is similar to that one, the difference is only that you have a second AP (on which you do not want the guest wi-fi, so it should not need to be VLAned).