Mi-Fi for educational use?

Hi does anyone have experience of setting up a mobile internet router for use in an educational setting?  I'm wondering whether there is anything I should be aware of that I might not have thought of before I go ahead..!

I'm considering buying a Mi-Fi router to allow learners to connect their own devices but keep them separate from the institutional network. The Mi-Fi would also allow us to take the internet to classes that are off the main site. 

I'm thinking of perhaps finding one that allows up to 20 devices to connect so that potentially a whole class could be using it but in reality most of the time it will be used by a handful of devices when individual learners access the computer room on a 'drop in' basis to get help with specific online tasks.

The data SIM, contract and amount of data we'll need I think we'll have to figure out for ourselves - I'm in the UK and most of you aren't, and we don't really have any idea how much this will be used until we try it.  But I'd be really interested and grateful if anyone has any insights to share into things such as monitoring usage and privacy, establishing terms and conditions of use with learners, managing passwords (I'm thinking that with a limit on how many can connect, I want to ensure those needing it for classwork or work with a tutor/volunteer in the drop-in can connect and not allow others who have connected once to reconnect automatically every time they walk in the building - so do I keep changing the password, or use an app to manage the connections... seems like it might get time consuming)... or other things that I haven't thought of yet?!  

Are there any published resources that address educational use of Mi-Fi that anyone knows of?

 

Thanks in advance!
 

Jo