I'm looking for a system that can help with assigning volunteers to events. We have a small museum that's open on Sundays, and need to have two volunteers there every week. So I'd like to offer a (web-based?) registration method where people can volunteer for these two "slots".
There are several similar questions here on superuser.com, but I have one additional requirement that none of the other authors needed: The system must alert us in advance if the two slots of an upcoming weekend are not filled yet. Ideally, it should send an email stating something like "there's an event coming up in three days, and only one person offered to host it yet".
Thanks in advance for any hints!