Phone for Wifi tether (prefer no rooting/jailbreak)

Just found out my niece got in trouble with my brother for using a ton of data watching youtube and netflix using cellular data.

I've looked around for a solution and this what I came up with the most cost effective methodology to hook her IPad up anywhere she is wirelessy.

1) Metro PCS in souther california unlimited data plan $60 a la carte without using their paid tethering service which WILL throttle after certain data level used regardless if I'm "unlimited" data plan.
2) use program to enable wifi tether (which will not trigger throttling), so far I've found:
This is the one I found that seems to work for that phone and carrier -->Foxfi

3) This is the phone I will give her: Inexpensive, has 4GLTE

I am very open to suggestions here as I have not committed to anything yet.

So if you have a better cost effective strategy that consistently works and doesn't require a ton of technical know how then please suggest.