The solution is to use either Feedcombine, Chimp Feedr, or Yahoo Pipes to merge the feeds into one single xml link as I learned here:
http://www.creativeramblings.com/3-tools-to-combine-multiple-feeds-into-one/
I tried all three sites and settled on Feedcombine as Chimp Feedr didn't seem to work on Feedburner, and Yahoo Pipes was displaying the posts in the wrong order.