Never mind. I got it working (after installing some needed drivers/files)
My /etc/config/wireless looks like this now:

config wifi-device 'radio0' option type 'mac80211' option path 'platform/ar933x_wmac' option htmode 'HT20' option channel '3' option hwmode '11g' option txpower '18' option country 'US'

config wifi-iface
option device ‘radio0’
option network ‘lan’
option mode ‘ap’
option encryption ‘psk-mixed’
option ifname ‘wlan0’
option wds ‘1’
option key ‘1234567890’
option ssid ‘AP_2.4Ghz’

config wifi-device ‘radio1’
option type ‘mac80211’
option channel ‘40’
option path ‘platform/ehci-platform/usb1/1-1/1-1.3/1-1.3:1.0’
option hwmode ‘11a’
option txpower ‘23’
option country ‘US’
option rts ‘root’

config wifi-iface
option device ‘radio1’
option network ‘lan’
option mode ‘ap’
option encryption ‘psk-mixed’
option key ‘1234567890’
option ssid ‘AP_5Ghz’


Only problem (for now) is when I scan with radio 1 (the 5Ghz one) I still see the 2.4Ghz AP’s.