you could try the CamaC IP Camera FTP and remote viewing service I'm currently developing.
This would give you a historical record of all uploaded pictures and will automatically delete old files to maintain the disk quota.
I don't have the concept of a guest account or link yet but this is on the to do list. So currently would have to share the account details with all the members
Run the demos or create an account at
https://app.comsci.co.uk/camac
Currently free while in development and probably only about £10 a year for a low data rate application as yours
Simple to access historical events
Your data is safe and secure. (Encrypted via HTTPS and FTPS)
Access from anywhere with Internet and a browser.
No router configuration required.
No static IP or dynamic proxy requirements.
No vulnerabilities from open network ports
No software or plugins to install
No DVR video recorder required.
Data is preserved in the event of camera theft, damage or power disconnection
Performs better than other remote viewing solutions where bandwidth is limited (E.g. poor wireless or mobile signal)
Automatically deletes old pictures to maintain disk quota