After receiving SIM cards for my iPhone 5 and iPhone 6 and iPad 2, I put them all in. The iPhones didn't work right away, but after calling and they making changes, they worked fine. The iPad did not, and after escalation with Consumer Cellular support, they quickly gave up and said iPads are not supported. HOWEVER, using the APN Changer tool available at the following location...
https://www.unlockit.co.nz/unlockit/
...I was able to select Consumer Cellular as my carrier, and it generated an APN configuration file that Safari was able to interpret as a configuration file and the iPad was able to import it. Once imported, the APN settings were updated and my iPad 2 was able to get full 3G on the Consumer Cellular network. I can't speak for LTE, as my iPad doesn't support it, but I know others that have successfully used this tool on iPhones before Consumer Cellular had automatic configuration working, and they had no problem accessing LTE. Apparently, this tool has been around for a while.
I can't vouch for author of this tool or verify that there's nothing else nasty in it, however given my choice was between a cell-unusable iPad or giving this a try, I tried it after fining no suitable alternatives. It does allow selection from a bunch of carriers, so I suspect this would work well for other networks besides Consumer Cellular, provided they are in the list.
~Michael D. Bailey