Just use the phones. They 'should' have the same access to 4G if that's what you can get where you are at.
Stand alone MiFi hotspot 4G does not work any better than my old Samsung phone when connecting to it.
It's mostly about the plan you get.
My phone does not have much data, as I don't really need that, but it has enough to connect to it if needed. As long as you have Cell service where you are!
Antenna's don't really work in my experience.. My Office allows me to use their MiFi when I'm out of the office.
If I'm out of Cell range on the phone, the MiFi is not any better, even with some external antenna's plugged in.
But, I agree, use your own "WiFi" anytime you are in a park that offers "free WiFi"... You will never be able to do more than browse Google or check email. Plus the security issues are too great to make it worth it at all.
Anyway, good luck! Mitch