backup and permissions

Hi, I'm working on a little backup utility for a desktop application. It's
going to execute pg_dumpall (-r) and pg_dump, but first I have to deal with
the permissions needed to do that:

1. Users (pgsql roles) enabled to backup would be superusers all the time.
This sounds insecure.

2. Users will get superuser access through a security definer function just
before the backup, then they'll be nosuperuser again. An interrupted backup
process would be dangerous, but I could check whether or not this clause is
enabled, every time a user connects. Still risky.

3. Users will just be able to read every object in the database, and
pg_authid. I've done some tests and this seems enough.

I need some advice to choose the better/safer option, what would you do?

Thanks in advance.