The idea is really nice, but AWS sounds overkill? Using the same Python file with an Sqlite db (or a text file) and using an API like Mailgun to send the emails, it could run on any machine with a plain cron job?
I built a comparable system that sends me an email every day that I can respond to, to maintain a journal; it works like described above and has been running for about 5 years now with zero downtime.
Anyway the idea is really good!