A little background:

I live in a house where there are four adults. The owner, myself and a couple who are both 25 that moved in this past September and want to get married this coming April. The couple are getting married in the township courthouse on a Wednesday with a home gathering to celebrate the following Sat./Sun. I am on a fixed income with SSDI but would still like to give money, I just don't know how much is appropriate given the circumstances.

Any advice?