I am building a website for a sports training company. They would like a family to be able to log in, add family members to their account (their kids) and then register those kids for classes and training sessions. I have found some good plug ins for the registration part (like Event Espresso) but how would I handle them being able to add "kids" to their wordpress profile and then register those kids for events? Ideally, they would be able to filter for each kid to see what classes they are signed up for and see payment history etc. Too big for a plug in?