Best way to collect user information – forms?

Hello, I run a soccer league for kids and am currently using a WordPress 3.0 site for parents to sign their kids up. I’m pretty new to WordPress and have figured out a way to do – more or less – what I want, but I’m not sure it’s ideal.

Basically, I’m using WordPress for high-level content management (linking to other sites and posting information such as rules, schedules, and field maps, etc.), but then I’m using Google Docs (I embed the Google Docs hyperlink in a WordPress page) to display a form that parents use to register for the league (we collect info like parents’ names, kids name, age, school, etc.). This works pretty well – Google Forms are *easy* to create, the information is stored in a Google Spreadsheet behind the scenes, and Google Docs will automatically generate some statistics for me – but seems a bit goofy for a number of reasons:

1. The form requires a long scrollbar (we need a lot of information, waivers, etc.) and is not very user-friendly.
2. Parents registering multiple kids have to enter all of their information every time (i.e. they don’t login and the form won’t auto-populate with previous information).
3. I’d love to add PayPal capabilities but it seems a little difficult to manage through the Google Forms – handing data off, providing users confirmation that their registration was received (and paid for) aren’t seamless
4. Since the information being submitted is somewhat sensitive, I’m restricting access to the spreadsheet containing registration information. Unfortunately, with this approach, there’s no easy way to send users an email confirming their registration. In addition, if I restrict access to the spreadsheet, I can’t show all the great statistics about who’s registered to play.

I’m sure there’s a better way to do this, but I just don’t know where to start. The number of Forms plugins is quite overwhelming, and I’m not sure that’s really what I need…

What I want:
1. Ability for users to enter information
2. Ability for information to be stored in a database, spreadsheet, etc. (and ability to extract this information)
3. Ability to populate a form with existing information (i.e. if a parent is registering multiple kids, the parents’ name/address/phone should auto-populate when they register the second child)
4. Email the parent that registration was received (or some type of transaction ID for the parent to record)
5. Ability to pay online (PayPal or other)
6. Email the parent to confirm that payment was received (or some type of transaction ID for the parent to record)
7. Statistical information about registrations received (total players, number of boys/girls, number of 1st/2nd/3rd graders, etc.)

Help? Should I continue down the road I’m on (working with Google Docs) or is there a better way to do this in WordPress? Do I need to develop my own forms (and if so, what books/resources/tutorials should I consult to learn this) or are there some plug-ins I should investigate further (I’ve looked at Contact Form 7, Events Registration, Flexi Pages, FormBuilder, etc. but either I’m not spending enough time with them or they’re not as simple as I need them to be…)?