You want to spend your 5 hours in the museum as unencumbered as possible. Smaller museums have lockers. Often there is a one guilder deposit required to use the locker, so carry some pocket change including a one guilder piece. If there is no one attending the locker, it's likely you need to insert the required coin into a slot on the inside or outside of the locker door. Once you have all your gear stashed it's time to check a couple more things before you tour the actual museum.
Museums commonly have very passable lunch rooms or cafeterias.
I remember having an excellent uijtsmiter at the Frans Halsmuseum in Haarlem. The woman working the lunchroom was alone and very busy with many customers, but everyone was patient and congenial. Now make any required pit stops and head into the museum gift store. Aside from your basic tour book for about ten dollars, most museums have published inexpensive full size paperback books showing the elements of their permanent collections. These more extensive catalogs are well worth the higher price of twenty to twenty-five dollars.