The roles of family during the wedding

How do you fit in family when you don't have all the aspects of a traditional wedding?

Okay, the church part is certainly traditional. Interestingly enough, our priest informed us that the giving away of the bride is actually not a church tradition and was actually started by royals in England. He did say we could have representatives from each family either say something or walk with us.
Our situation is delicate since Mr. Chic 'n Cheap only has his sister left. His dad fought a valiant battle with cancer and it ended a few months ago. I used to be a peer counselor at school but I still don't know how to handle tragedy on a personal basis. I just try not to do anything that involves joint parents (e.g. dance with the parents) or just ask him. It's not an easy thing and the least we can do is include a note in our program and try to set up American Cancer Society donations.

But he will be walking in with his sister. I will be walking in with my parents.

Mr. Chic 'n Cheap's sister is a little shy so we are not asking her to do a reading. But her daughter will be our flower girl/ring bearer.
My brother will do a reading.
My effervescent cousin will be the MC/videographer for the night along with her brother.
My mom is planning the rehearsal dinner (with great discounts based on her connections).

It will be fun and each person is helping us in a way that are suited to their skills and personalities.

How is your family going to be involved?