OpenWrt for your RT3200 uses DSA for the switch. OpenWrt for your ath79 target dumb AP's uses swconfig. They will set up a little differently, and most tutorials you find will be for swconfig. Don't worry - they work together fine.
First, I'd suggest going for some basic background information here: DSA Tutorial Information. Followed by this simple example (not what you want, but the example will perhaps help you understand setting up your network): Example single untagged VLAN SHO setup.
What you want to do is set up all the VLAN interfaces on your RT3200 and give them all a DHCP server on your RT3200 as well. For extra credit, make your RT3200 the time keeper for your network (ntpclient so it gets time, and ntp server to your AP's) and tell your AP's (ntp clients only) to get their time from the RT3200 (ntp server). Same with DNS server-tell your AP's that your RT3200 is the DNS server for the network. You don't want four different devices all trying to do the same thing on your network. You will find it much easier to have your RT3200 manage your various network needs all in one place. Then send all those VLAN's tagged out of the three ports your dumb AP's are plugged into and down the Ethernet cables to the dumb AP's. You have multiple VLAN's going down the same wires, so all but one of them needs to be tagged to keep them all separate-no way to tell them apart otherwise.
On your dumb AP's, you'll set up a DHCP client interface (no DHCP server on your AP's - that's on your RT3200 already!) for each VLAN and connect that interface to a bridge for your wireless. Then set up wireless interfaces with unique SSID's for each VLAN and attach each to its corresponding network interface.
Finally, you'll need to set up firewall zones for each VLAN on all your devices so that each VLAN can get to the DHCP and DNS server on your RT3200. Otherwise, all those VLAN's can't get to the internet and nobody's happy.
Done. Clear as mud, right? Since your setup is so close to mine (DSA main router, 4 VLAN's, and 2 swconfig AP's for me), I'll pull my configuration files out and post them for you in a separate post.