Refresh my memory, can iPhone 1 send/receive MMS if it's on the most current software version? I thought I could way back when, but can't remember for sure.
MMS on AT&T (the only official US carrier at the time) came out in late September 2009. The current iOS version was 3.1.2, which was supported on the 2G iPhone. MMS did work on Edge. I'm 99% sure MMS worked on the 2G iPhone at the time, so as long as the 2G is on 3.1.2 or later right now, it should work.