We go annually for a gaming weekend, hotels in the middle are notably more expensive than the ones 5-7 miles out so it depends what you are doing. The public transport network is very good and there are travel cards so a cheap option is to stay in a hotel on the outskirts and train or tram in and out. Takes around 30-40 minutes but at least one of the party needs to be capable at the end of the night. As neither of us drink (or otherwise partake) we drive over from Kent, it makes a long journey of it but means we can carry bikes in the car. Then we cycle in and out. Some hotels hire bikes, but they are quite expensive. There are cheaper places in town. It's probably be cheaper for us to fly and hire, but we like having bikes we know, plus we make a thing of the journey both ways. We couldn't visit Dunkerque
Decathlon if we flew. If you are intending to get variously bladdered then staying in the middle makes sense. You can rent apartments, sometimes on boats, if there are a few of you to drop the cost down.
If you want to go to see the Anne Frank House, book in advance.