To Membership Or Not To Membership

Hello, everyone!
I am a fairly novice developer with some questions regarding ASP.NET Membership. Here is my situation. I will be developing an MVC application and have been working though Sanderson's "Pro ASP.NET MVC 2 Framework" book. The application I will be developing has no eCommerce aspects and will merely serve as a social networking tool for a local school. As I have been considering how users will log in, register, etc., I have come across a few snags.
I do NOT want to make use of the UserName field which comes with the membership provider. Users will log in using their email addresses.
I DO want to make use of FirstName and LastName fields, among other things which do not ship with ASP.NET Membership.I plan on utilizing Entity Framework to a great extent and I do not like the idea of having two redundant tables for my users (One custom table used by EF, and the others being aspnet_Users/Membership tables) just so I c ...