Doc - If you can pick up your car at one of the intown locales you'll save a good bit vs. getting a car at Schipol . We've had the best luck with this outfit.
http://www.e-sixt.com/
as for trips ...We've enjoyed driving thru NL the last several Junes . For the CS Scene Leeuwarden is our favorite of the provincial towns we've visited. For history and architecture maybe Middelburg or Zutphen (both have nice CSs-see reviews on this site) Have you been to Haarlem ,or Utrecht ?
If you opt for Fryslan- Hindeloopen,Dokkum and Harlingen are great little towns for daytrips. Harlingen is on our list for a revisit this summer (1 CS )
Valkenburg way down in Limburg is a nice ,though very touristy town near Maastricht ,even got a hilltop castle .Alas no CSs,but close enough to Maastricht for an easy train daytrip. If you really want to get out in the boonies theres Bourtange on the German border . A restored 1700s star fortress town ...anyway I Could go on and on about all the cool NL places we've visited . Would be glad to tell more about hotels etc. if you decide on a place we've visited ...have fun planning .