Do you both have Apple devices with FaceTime? Easy to connect that way. I use it regularly from Europe and Asia with hubby and adult "kids".
I have T-Mobile Magenta. On recent trips to Europe, I've called an elderly relative's land line multiple times. I believe the international voice call rate is $.25 per minute. It didn't break the bank for me - I didn't bother monitoring call length. Call quality was such that the relative didn't know I was out of the country. Relative would not be able to manage What'sApp, Skype, or other free app connections, not even a smart phone.
My plan charges the $.25 per minute cell to cell, even when on family plan.
Don't apologize for asking for tech instructions - even when using your own phone. I think it probably happens to most of us over the age of 30! It's too easy to overthink or miss an iteration of updates, or the newest "hot" method for accomplishing something.