People usually do what they’re told in church. Just announce it before mass and have the ushers give them a stern look if it seems they’re violating it. Plus, the other people around them won’t like what they’re doing and the disapproval will probably work to enforce it.
Even non-Catholic visitors are ok with rules like this. When tourists come into the Cathedral and I’m giving tours, they always ask if it’s ok to take photos. It is, so I can say yes, but if I told them they couldn’t, they’d be okay with that.
We have to give people a little more credit, IMHO. They just need to be told what’s expected of them.
You got that right.
Even my parish church does ask folks to shut their cell phones off for the mass worship, although some folks forget that from time to time.
My present parish priest will be leaving at the end of the month and whoever comes in as new priest afterwards, I would not be surprise that things will get stricter, got to wait and see.