Dreaded tourist post

Greetings! Tourist heading to the Netherlands for first time at ripe young age of 68 (gulp).

I would appreciate knowing a couple of gems you would recommend to someone whose accompanying family of three (wife, and mid-20's daughters) might like in terms of gardens, markets and must-see landmarks. Just as valuable - maybe one to two spots that only meh.

This is our first stop - London and Paris afterwards - but as I am the one who picked the Netherlands I want it to make maximum favorable impression. We'll be there early May for three nights, four days. Thank you so much!!