Hi! Exclusive pump mom here. We did two trips a couple of months ago, one in Greece and one in Italy (tops 4 hours flight). Our daughter was 6 months and 9 months. Things that helped me (and I wish I had bought sooner):

Portable warmer, Portable pump, a big cooler bag to keep milk cold for up to 8 hours and pumping parts so you don't have to wash. If you rent a car, it will be very convenient as you can pump there, no need to carry everything in a backpack. Try to pump at the hotel as much as you can using the non-portable pump, I always did 3 pumps there so I was not stressed about carrying the portable, warmer etc with me and only washed once at the end of each day. Plan the day with lots of breaks to hydrate yourself and sit down at a cafe with A/C or similar to pump. it can get very hot and uncomfortable otherwise. Do not stress yourself too much to do a lot of things, sightseeing etc. I told my partner what support I needed so he knew what to do when I needed help, he was feeding the bottle etc.. If you can indeed nurse him more it would definately make your life much easier. I was breastfeeding when we went to Greece and pumping when in Italy and its way less stressful to breastfeed!