Iphone 6 Plus Verizon traveling internationally

I have a 6+ with Verizon and I am going to be traveling in Europe for a month. I have purchased the international plan they have with 100mb data, 100min, and 100 sms. Given that I was wanting to be able to iMessage to friends and family back home in the USA and was wondering if I left data roaming on, but turned off the data for each individual app would that stop all other data flow other than iMessages? Also, I am aware that iMessage works over wifi, but just in case I'm not able to get wifi where I'm at. Thanks.