I've been thinking along the same lines.
I haven't used these guys
http://www.myphotofun.com.au but might be worth a look.
I was thinking it might be easier to have the prints done on A4 paper ( maybe and not Photographic paper. But I don't know what the quality will be like in the end result.
I've already found a Photoshop template for next year. I'm looking forward to other DLSR users thoughts.
Cheers