Netherlands-car rental for days outside of Amsterdam

Traffic , yes but not horrible. If you are comfortable driving in cities and on Interstates you will be fine. Be sure to take a GPS loaded with European maps . It will really help you to not miss some confusing exits and turns. I agree, a car with kids works best for us too. If you have time, go to Gouda and Den Haag too. Others will disagree, but we felt that one full day in Amsterdam was plenty. We enjoyed one day in Delft and Gouda, another in Alkmaar, and Markham. Another at Muiderslot castle and in Den Haag. Parking on side streets or in a parking garage was easy in all these locations. Have fun!

A couple of notes. Yes, traffic in the Randstad area of the Netherlands is bad, probably some of the worst in Europe. There aren't really any flower fields that you can "tour", as such. If you drive around some of the rural polderland, you'll see the fields. You may be able to walk along the road, but most of the growers discourage tourists from walking through the fields There's enough stuff to see at Keukenhof to keep kids entertained. You obviously know your kids, but my guess is that a flower auction will kill them with boredom. I wouldn't go out of my way to visit Arnhem. There's hardly any traces of the old city left from before WWII, and the only indications of the battle fought there are a few muted monuments. EDIT: Oops, forgot about the open air museum that James mentioned. In that's what you want to see, then ignore my comments about Arnhem.

For the places you list, a car won't give you any more flexibility.....take the train.