Phone Planning for Cruise is making my head spin a little

While I've always been anti-phone for my cruises, for this trip I unfortunately have an important need to be connected with family back home while on this one. Here's my plan so far, but it does have my head spinning a bit. Can anyone take a look and let me know if I'm missing or mistaken in anything?

All 3 parties have iPhones and I need the ability to text frequently (some with photos) and call infrequently.

1. Will the below allow me to do all of the above?
   • I've purchased an International Pass to cover calls, texts & data while at the ports with my phone company. I plan on getting the Premium Wi-Fi plan with Carnival (it was only a $10 difference between value and premium). Will be using the Carnival app to communicate with family on the cruise.
2. How to manage my phone:
   • When leaving the ports and out at sea: Keep phone on airplane mode with wifi turned on (airplane mode turns off data roaming); turn off automatic app store downloads & background app refresh. This will allow me to text and receive texts with photos & use data. I just can't make phone calls I think.
     • Not sure if I should use iMessage or SMS?
   • When at ports: Basically reverse the above... take phone off airplane mode, make sure data roaming is on. This will allow me to use my phone company's int'l pass to text, call or use data. I won't have to worry about finding wifi.

Appreciate anyone's feedback!