I'm buying 4 iphones on verizon. How much data should I buy for the group?

They sell data plans in increments of 2gbs, 4, 6, 8, 10, etc. I have Wi-Fi at my house and spend most time at home. Does using Wi-Fi use up the data service? What would you suggest?

Using Wi-Fi does not use up the data service. You use your data when you are on the internet when not connected to Wi-Fi. I recommend you get 2GB, in fact, most people don't even use 2GB of internet each month, so that will definitely be good.

You could get away with using 2GB of data because if you're at your house connected to a Wi-Fi connection you will be using your own internet. Verizon only charges for data if you use cellular data.

To prevent going over your data limit:
1) Go to Settings on the iPhone
2) Go to General
3) Go to Cellular and click on it
4) Turn the slider to off

*Do this once your device is connected to a Wi-Fi connection*