DON’T PLAN THE EXACT DATES AND TRY TO FIT THE FLIGHTS TO IT! Be open to a general time frame.
Sometimes I pick, sometimes they pick, sometimes we figure it out together. Oftentimes, this is based on the cost of flights and the time of year. I am always asked “how did you find flights that cheap?!” We set nothing until we find the flights. We usually look at shoulder seasons (April, May; October, November) because it’s much cheaper and there aren’t nearly as many people at the main sights. Until recently, this worked just fine even though the boys were in school. However, with high school having higher stakes and it’s harder to make up, we will have to start traveling at times that fit between school and baseball.
That said, let’s look at the previous travel dates. We have done two major trips to Europe, both at the end of October which worked out perfectly and our flights ended up being ~$300/person round trip. Pick a time of the year, use Google Flights and Hopper to be able to figure out what the best departure and return dates are, and then plan the trip after that. I will say that Hopper used to be amazing and much more flexible. Lately, I’ve been using Google Flights the most since you can use the price grid and move around dates to see what the best deal is and then set a tracker for that time or for anytime for a certain amount of days/weeks.
From the US for European vacations, we’ve have flown in and out of Paris for most often and Munich for the other because that was the cheapest and then it’s quick and cheap to jump on a European airline from there. We have flown EasyJet and Transavia and it has worked out great! I will say, Transavia appeared to track cookies and the prices would go up if I didn’t book immediately. When I cleared cookies, it would go back down.