If you are moving around a lot, I would suggest verizon or att as they have better coverage compared to the competition. Since you really only have 1 site, I would check the coverage maps and ask your nieghbors what they have and how many bars they get.
An air card is a simple way. We don't bother with a docking station or external antennas. Unless your place it in marginal coverage, they aren't worth the trouble and the card will already handle 5 devices at a time.
Another option is many smart phones have the option to operate as a hot spot which is essentially the same function as an air card. Make sure you can make calls while the hot spot is in use but that is becoming less of an issue with newer phones. If you both already have a smart phone, this is probably the best option (if you share a single phone and one of you goes to the store with it, you lose internet access, we ran into this when I had a work phone that didn't have a hot spot and didn't want a second phone, so we kept the air card)
With either option, you will need to keep the device plugged in if you want to use it for any significant length of time.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV