Rental from Amsterdam

hey hey mschoeffler
what are your dates, how many is "my family" if kids how old? do you have a place to stay? look at the cost if picking up car in one country and returning to another, do you need an IDP (internationaldrivingpermit.org) for renting?
looking at airbnb/vrbo for your family, much has been mentioned about illegal rentals and cancelling at last minute. when we were there we rented a houseboat in amsterdam (bookahouseboat.com or houseboatrentals.amsterdam)
hope you find something and enjoy your time.
aloha & hauoli makahiki hou

Can you be more specific about the WW1 and WW2 sites you want to visit? Do you have special places in mind or things you want to see, or do you need more info about what to see? And how many days you think you will need for this?

For WW1 is Ypres (or Ieper in Flemish) the obvious place, but the WW2 sites are more spread out if you go to Wallonia for the Battle of the Bulge and want to include for instance Luxembourg. Using Amsterdam or Haarlem as a base to visit these sites is anyway not very efficient. Not only the distance you have to cover, but also the many road congestions you have to deal with will consume too much time. So basing somewhere in Belgium for the time needed to visit the WW sites is necessary.

But again tell us more what you expect or want to see to start with.

There are four of us, including two young adult sons, flying in and out of Amsterdam during spring break. We’ve hit the highlights before and want to visit Ypres from Bruges, and then Waterloo on the way to Bastogne. Hence the need for a car. Logistically, parking changes our usual train and backpack pattern of travel. My concern is the best way to start and finish in Amsterdam and avoid driving and parking in Amsterdam. We enjoyed using Haarlem as a base for Amsterdam previously, but don’t know the rental car aspect.
Thanks in advance.

What about taking the train to Brugge and rent a car (and drop it off) there?