Now that both phones are paid for, the bill is an additional $50/mo lower; mind you, we paid $650 apiece for the phones, but there were cheaper options if we wanted them; that's not relevant here, though, since you have to buy your phone on Cricket, as well.
I think you're getting the current Cricket, a wholly owned subsidiary of AT&T, confused with the old Cricket (a regional CDMA carrier). They allow you to use any AT&T locked or unlocked GSM phone. The coverage is the same as AT&T's native (non-roaming) network. I use a iPhone 5S originally from Verizon, on Cricket; I certainly didn't have to buy one of their phones.
According to their rates chart, they don't offer unlimited.
T-Mobile and Sprint are the only games in town if you really need truly unlimited data. Once that becomes part of your selection criteria, you know what your options are.
I say nearly because Cricket will cut you off after 5GB, while T-Mobile will throttle, and Cricket no longer offers tethering, so really. No. they're just not a viable option.
Cricket throttles at 128Kbps, the same throttle speed as T-Mobile and Sprint. It's just as unusable on all carriers. You are correct, however, that Cricket does not offer any form of wireless hotspot/tethering add-on. They also don't do anything to stop you from tethering if your phone natively supports it, or if you've enabled it by way of rooting/jailbreaking.
More-or-less, MetroPCS (which is now a wholly owned subsidiary of T-Mobile) offers exactly what you're getting now on the same network, for $120/mo. That's two lines at the base price of $60/mo each, a $5 family plan discount on each line for having two lines, then a $5 fee on each line for adding mobile hotspot functionality to both lines.
What you'd lose is the ability to roam in the few places T-Mobile still has roaming agreements (looking at their map, I can't imagine where) and the ability to finance your next handsets. Is that worth $30/mo?