I take the train often for work, but when touring with the family it is a poor replacement for a car. Obviously the cost is cheaper by car with several people, you don't have to lug your bags on and off trains, you have food with you, you have baby items which are critical if you have a little one, and most important of all, you can stop anywhere you like. You don't have to pass by the things you want to see at high speed. You see a neat old church or castle, or an inviting park, you just pull over. And if you want to buy some wine or antiques, that can be very problematic by train.

But if your objective is to just visit a couple of city centers and you don't want to deal with driving, then sure the train is nice. I'm a very frequent business traveler on French, Belgian and Dutch trains and they work mostly ok.