You can log into the site and make small payments towards your final payment. People don't know you can do this, but I do it all the time. You have 4 weeks before then, so take the 331 divided by 4 and that's only $82.75 a week.
Log onto the site and make the smaller payments each week . . . you do get a 3 day grace period AFTER your final date before they cancel and keep the $100. BUT, I wouldn't test that!!
I do this all the time . . . monthly payments are easier for me then one big lump sum! List a few things on ebay, you'll have the cash in no time.
AS LONG AS the trip won't cost you or your family a hardship, then GO! You have planned this for the longest time.
