How to handle an inconvenient but expensive and unrefundable gift?

For my birthday, my brothers got together and purchased me a round-trip ticket to San Francisco in August, to stay with an old family friend I haven’t seen in years.

Although I really appreciate the sentiment and expense, this gift came at the wrong time. I did want to make the trip to San Francisco to see this friend at some point in the next year (maybe around Spring 2014), but not this summer; I had other plans (a study schedule to prepare for next semester, a comprehensive workout regimen, volunteer work at the hospital, etc.). Regardless of my summer schedule, I would not have planned a trip for an entire week; 3–4 days is more my speed. To top it off, I just don’t have the cash for the expenses a trip like this generates.

So, what do I do? This gift feels very… “forced” upon me: the timing and duration of the trip doesn’t work for me, but the tickets cannot be refunded or exchanged (without a hefty fee, that is). I’m not a big traveler, but my brothers are and they are always on my case to travel more. I don’t want to insult them, but I am a little miffed by the imposition of a trip that I had no input on. Plus, I don’t want to insult my family friend, who was in on the plan.

I really have no idea what to do here.