Ask HN: Advice on creating a student tracking app?

At a nearby school, students are signed in as they arrive at after school care (time-stamp recorded), and signed out when their parent or other adult picks them up (time-stamp again). The adult also signs their signature at pick-up. There are close to 500 students and about 75-100 attend after-school activities.

Currently the time-stamps and signatures are done on paper (!!!), and I have been asked to see about implementing a digital solution (free). The person in charge has an Android tablet (HTC Evo View 4G) and there is WiFi available. The app or website should allow storing of multiple adults who can pick up a student (parents, siblings, etc), searching by name of either the student or the responsible adult's name, recoding timestamps and signatures, and be able to do some billing calculations or exporting to a spreadsheet.

How would you implement this? What language(s), technologies, and hosting platforms would you use?

Here is a little about me (though feel free to describe what you think would be the optimal solution): I have some fairly basic Android skills (you can see my app via my profile), so I am thinking a web application would be best. I know HTML/CSS/JS and a tiny, tiny bit of Ruby/Rails. I also found a few jQuery Signature libraries, which look very promising:

http://thomasjbradley.ca/lab/signature-pad http://keith-wood.name/signature.html http://willowsystems.github.io/jSignature/#/about

Any advice from my fellow Hacker News members would be appreciated.