Good place to stop en route from Calais to DLP, 3-4hrs + lunch?

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We have finally decided that we are going to stick to the Eurotunnel for our March trip, however, rather than a day trip in the UK on our way outbound, we are going to stop off somewhere between Calais and DLP for some sightseeing and lunch.
Just wondering where would be good and not too far from the route? Don't mind if it's near Calais or DLP.
Looking at the google route Amiens looks like it might be a good place to stop. But despite googling still not entirely sure what would be good for the kids, not interested in the zoo, can do a zoo at home, would like them to see something specific to France and local culture. Found out Jules Verne from there (could link to Discoveryland ) and hs house is now a museum, though still not sure how interesting it is for the kids.
Thanks