Help for site overhaul

Greetings,
I am very new to WordPress and am having great difficulty figuring out the best way to achieve my goal. I maintain a Lacrosse camp website where users can register their children for Lacrosse camps and clinics. I am looking to have users register for my website but I want to capture a considerable amount more information then just an email address and password. Please see below for a full project description

I want to add user registration functionality to the web site – (http://maddoglax.com/wp/home/) – so returning users don’t have to fill out this form – (http://maddoglax.com/wp/register-form/) – each time they register a child for a clinic as they do now. Then in the future if they want to sign a child up for an event when they come back “to register for an event” there will be a box where they can click on both or one of their children to sign up for that event. We are looking for something similar to the process on http://www.trilogylacrosse.com/. I also want the users to be able to pay via PayPal, Credit Card or eCheck.

I want to avoid outsourcing the project to a consultant so I’m curious if there might be a theme & plugin combination that would help me achieve this?