We would like to do a daytrip from Maastricht to both Amsterdam and Keukenhof. Considered renting a car to save some time getting to the gardens. After the gardens, considered driving to the Olympic Stadium and parking the car for a tram ride into Amsterdam to see the Rijkmuseum, take a boat ride, and maybe see the Anne Frank House. Too much for a day??? Is rental car a good idea???
It'll be a long day, whether by car or train. ViaMichelin gives some 3 hrs; the train (to Schiphol airport, from there with the Keukenhof Express bus) is around the same.
"Too much for a day???"
It sure would be for me! Keukenhof and the Rijksmuseum are both extremely popular (meaning often absolutely mobbed), and so they can be quite tiring - and that's not to mention the round-trip driving, all in one day. Could you spend a night near Amsterdam or Leiden, and return the next day? If you do, you'll have a much better trip. If you can't spare a night, I'd pick either Amsterdam or Keukenhof, but not both.
It is possible but tiring. You don't need a car.
Take a train early in the morning to Schiphol, where shuttle buses to Keukenhof depart. Time your train to arrive at Schiphol in time for the first shuttle buses of the day before the masses from organized tours arrive there. Be sure to buy your "combi-ticket" (shuttle bus + ticket) in advance, online, so that you don't lose time queueing.
Afterward, take the shuttle back to Schiphol, then go to Amsterdam. I'd not visit the Anne Frank house in the same day; it would require waiting in line after 3:30 PM or booking a timed ticket that would tie your plans. Instead, make the trip to Amsterdam mostly about strolling around than visiting another indoor attraction.
The last trains from Amsterdam to Maastricht leave around 10 PM and arrive past midnight.