Polite way to ask for a reference?

I'm applying for a volunteer position on campus and I need to give the contact information two faculty/staff members that are willing to be character references for me. I have two people that have been my references in the past, but I always asked in person. I'm not sure what to say in an email that doesn't seem rude. So far, I have:

Dear So and so,

I hope your summer is going well. I'm applying for [the organization]. [description of the organization and link to webpage]. Part of the application requires the contact information of a staff/faculty member who can be a reference for me. I was wondering if you would be willing to be to do for me.

Thanks,

My name

Should I add anything else?