I knew about both of these events well before booking my tickets, but I was concerned about letting these "less important" events delay my field work. In hindsight, two days is not a big deal and I think I'm missing out on some important networking by missing these events. In the case of the first event, my cohort is going to get up to speed on the methods for our project while I'm flying around and sitting in airports.
The SFC event is important for a different reason. In short, the reason I came to grad school was so that I could some day lead foreign study programs as a professor at some other Small Friendly College. I need to make my potential availability as a program assistant for SFC known, and this event would've been the perfect opportunity for that. I thought it would be lame to delay my departure by a day so that I could go to an event about Ukenzagapia, but that was silly.
Really though, there's no use crying over spilt milk and I'm trying hard not to fret about the things that are beyond my control to change (or not worth the $250 change fee). And besides, at the time of writing I'm already halfway there.