How Can I Get Gwen Stefani And Alyssa Milano To Attend As A Special Guests To A Charity Concert?

Hey everyone..I'm gonna be helping out and hosting a fundraising concert. The money we earn will be going to charity..we haven't decided to which organisation and things but I do know that we are gonna help people who really do need the help. I have been trying to get information on how I could contact different celebrities and ask if they could come and help out, but had no luck. We really want Gwen Stefani and Alyssa Milano to come as guests and maybe even perform and talk to everyone. I just need a way that we could get in touch with them. Please..no joking around. I really want to help people. This is for charity. Please help me.