Are you worried about the flight or the actual holiday? I took 13 month old twins on a 5 hour flight and have to say it was pretty hard work.
First of all check if you can when you have to give the pushchair up (if you're planning on taking one to the airport). Some will let you go to the actual gate, some make you check it in with your luggage (which means you are left for at least a couple of hours in the airport) without a buggy. We had 2 slings in the airport. We also took a little blanket so we could put them on the floor in the departure lounge and let them sit / lie with their little toys.
Are you intending on taking car seats too - we had to check these in with our luggage but was worth it for peace of mind when we got there. Just check whether they count in your baggage allowance or not.
On the flight itself, first of all, the babies will be on your knees (am presuming that you haven't booked them their own seats - they're normally expected to be on your knee) and you won't be allowed to sit next to each other (am presuming its 2 adults and 2 children flying?!) as most planes only have 1 baby oxygen mask in each row of 3 seats. We didn't know this until we arrived at check in, and only had one bag with all the baby related stuff in so sat either side of the aisle. There are pros and cons to this - obviously you're close enough to have a conversation, but with the stream of people / trollies walking up and down the aisle, there was quite alot going on and neither of them slept. However, it did mean we could stand up and walk them a little bit without disturbing other passengers (i.e. if you're not sat next to the aisle you need to ask to get passed). It is also quite difficult to negotiate plane food / drinks if they're on your knee and you haven't got anyone to hold them for a few minutes whilst you eat! I'd therefore have a few handy snacks ready that you can manage one-handed. Have everything you need (or might want) in a little bag by your feet 'cos if they fall asleep, you won't want to move for fear of waking them (or is that just me? ;-)!)
I also got myself in a bit of bother about their ears popping on the flight - they were on bottles by then so I had a flask of hot water that they allowed me to take through and I made 2 bottles up as soon as we got on the plane which we had intended to give to them as soon as we were taking off (only the water was too hot and they went mad seeing the bottles but me not letting them have it - perhaps make them up a little bit before so they cool down). That worked pretty well.
When you're actually there, am sure it'll be fine in a villa. We had a Shade a Babe which was great (we had a Nipper which we took with us - often the roads in Greece are more like dirt tracks so the NIpper was great) and the Shade a Babe kept them completely in the shade. We really enjoyed it and the stress was worth it!