60th B-Day

My brother and I have decided to celebrate our mother`s 60th B-day. We are inviting her family and all her close friends and also some close co-workers. We are planning on having a dinner party at a fancy restaurant in our town. We figure that we will have 3 choices for the meal that each person can pick from. We also wanted to some how ask for a $10 donation towards the dinner, thus this being their gifts towards our mother along with their attendance to recognize her 60th. How can this be worded to sound tactful? Please any suggestions are welcome.