Shelly, you can likely go with a smaller data plan, and set notifications for usage thresholds. We did that with a shared plan, and once on vacation we got notification due to Andrew's LTE usage. I called Verizon Support and for a flat fee added a one-time 2Gig extra (and as Mike points out above, the rates can be higher if you just let it go over and bill per Gig), which they set back to normal for the next billing period. Pretty easy.
I've actually been pretty lucky with Verizon support, I've heard some tough stories. But always pretty good for me.
EDIT: 1) if you consistently hit the thresholds, just bump up the plan permanently, and 2) make sure under your plan you can do the one-time bump and reset for the next billing period