In planning our time in Amsterdam, we've planned a day for The Hague/Delft. Should we also plan a full day for Haarlem?
Haarlem is a very pleasant place. You can easily pass a day there; however, it isn't large, and you certainly can see most everything there is to see in a few hours.
Rick is big on Haarlem, but I think that except for the Hals museum, it's completely missable. We just returned from The Hague, which we enjoyed, but Delft is much more important to visit. One tramline connects Delft and The Hague, as well as the railroad. It sounds like you don't have time to consider Kinderdijk or Keukenhof.
My husband and I spent part of a day in Haarlem a few years ago. We loved the town. We were inside the church and one of the locals who talk to tourists told and showed us what happened to the bones of those whose families didn't pay rent on the cemetary plot that was inside of the church. If you go, be sure to visit the Ten Boom house. Corrie TenBoom and her family hid Jews and Dutch resistance fighters during WWII and were caught by the Nazi's. It is a facinating story.
I shouldn't put words in James' mouth, but we returned from Amsterdam yesterday. It's much more crowded and dirty than our previous visits 25 and 13 years ago. But it is still an unmissable, vital European destination. It has the best architecture I've seen in the Netherlands, and like Venice, it's starting to sink! (No, really a little bit.) It wasn't impossibly expensive for middle-aged adults. And there were plenty of geriatrics with name tags and tour leaders in Amsterdam. (n.b. I'm 60.)
Have you given any thought to Gouda? We spent a nice day there wandering the back streets and visiting two cheese shops. The proprietor in one of them told us there is no such thing as Gouda cheese, but there is cheese from Gouda. The Dutch pronunciation seems to be "hooda". There are some nice cafes, and less tourists than in other towns we visited.