Don't bother stopping at Flipper McGills unless you actually call and get him on the phone to make sure he is open that day. We made a trip there a month back and they were suppose to be open and they were closed. Neighboring businesses said his hours of operation are not reliable.
1up and 2up are 21+ and you need ID even if you have grandkids.
Between Boulder and Golden is the Rocky Flats Lounge. Friday fish fry and big game day Packer bar with brats, burgers and curds.
http://wpdupdates.wordpress.com/2008/05/20/denver-co-and-surrounding-area-pinball-locations/