If you have a Verizon Wireless web site account you can monitor and check on your prior months' data usages. If you call or visit a corporate store, someone can also assist with determining how much your data usage is as well. I was on the more everything plan with 3 smartphones, 10GB data shared, and unlimited text and voice minutes for right at $200/mo including corporate/employer discounts. I switched to the current no contract plan, 12GB shared data and saved $60/mo. While there are some people like dahkota that are using lots of data, most people just don't so there is little to be afraid of by losing the unlimited plans.
This would be your cost under today's plans:
Smartphone 1: $20
Smartphone 2: $20
Dumb Phone: $5
Mifi: $10
That's only $55/mo and you pick the
data amount you need in $20/mo increments. Even at 18gb/mo for $100, that's only $155 total for you, a great savings from your current costs. Plus you get unlimited texting and voice minutes, even if you aren't using that today.