Hi C.,
It's been a very long time, but your question brought up so many memories I had to answer!
I was 11 years old when I was in Greece, and that was in 1973. Yes, we had an infant--my baby brother who had been born a few months before in Saudi Arabia, where my family was living for a couple of years. I wouldn't say my parents were "unprepared", given that we had, at that point, spent a year abroad, but none of us spoke Greek and none of us had ever been in Greece before. Also, we had certainly never experienced travelling with an infant in a foreign country before this trip.
We travelled in our brand new Volkswagon camper--yes, it was a beautiful '73 camper! Wish I still had it now! It was well before anyone ever even thought of carseats, certainly not the obsessiveness we all have with the illusion of "perfect safety" we all are inundated with now days. My baby brother travelled in what we called "the baby box", a bright red vinyl travel bed with handles that we would strap to the seat behind the driver's seat in the camper. We travelled the Autobahn and all the tiny, winding ancient roads of Europe with this arrangement and everyone was just fine.
The one thing I would absolutely recommend is a good stroller. It was the Europeans who invented the "umbrella" stroller--back when I was pushing my baby brother around Athens, these were a brand new thing. My mother said over and over how grateful she was that she had one! Make sure whatever you bring (or buy there) is lightweight, easy to fold and carry with one hand--important if you are juggling an infant, a diaper bag, and public transportation all at once--and very compact when folded. Also look for wheels that will manage cobblestone streets!
As far as your husband is concerned, I'm sure you are feeling like he is vastly unprepared because you speak Greek and have been there many times and he has not, but believe me, American tourists manage to navigate Greece all the time--it is a beautiful and open country, very ready to receive Americans who speak only English. It was in the 70's and I'm sure it has gotten even better since then. We did fine and not one of us spoke a word of Greek--until the college students on the beach at Alexandroupolis taught my brother and I to say "Opah!!" at a local wine festival.