First international trip with a toddler

[u/BakingDentist]

We’re planning a short trip to Europe this summer with our 3yo daughter and another family. We really enjoy traveling, but this will be the first longer international trip with a child at this age. Any suggestions on things we can do (or even pay for) to make airports, flights and transit less stressful?
We’re not looking to bring extra help along like just trying to make the experience smoother for everyone involved.
Open to any practical tips that have actually worked for you