Charity Website

Hey all! I’m a SysAdmin by trade and I’ve been asked to set up a website for team registration for a charity kickball event benefitting the Special Olympics. I’m in a little over my head here and hoping somebody would have some tips for me.

Basically, I need to have a form that takes in basic information (team name, email, phone number, etc.), jersey size (individual), jersey color(group), and then calculates the amount the team owes based on the jersey selections (some jerseys will cost more than others depending on size, color, and style). There will be one registration form filled out per team, so they will need to be able to indicate the number of team members and select a jersey size for each member.
Finally, the form will also need to be able to accept payment based on the figure calculated from the jerseys.
Any suggestions on how to accomplish this? The site will be hosted in conjunction with the city’s website, if that helps.