Do the 2100s support etherchannels (lag)? If so, it'd be easier to give the 2100 a trunked etherchannel.
Static ip addresses for APs is nice for monitoring, but it's not necessary. Our dhcp servers are setup to always give the same ip address to our APs when/if they dhcp.
The dynamic ip address is mainly used for dhcp-relaying. So you'll see that as the dhcp-relay agent in your dhcp logs.
Assigning 1 interface per wlan is the normal way. You can get fancy and use a single SSID with AAA Override and have a radius server dynamically assign each user to a specific vlan/interface. But I don't know if you want that headache. :-)