I found Frenchman's Bay West Park by chance, at the end of a cliff trail off Petticoat Creek Conservation Area. Walking along the waterfront, I came across the park's secluded beach. The sand was fantastic. The waves were great. Not many people seemed to have found this gem. Despite the fact that it was a gorgeous Saturday, there was still plenty of free parking spaces in a parking lot off Beachpoint Promenade, just before the park's lovely beach, and along the dirt road between the bay and the lake (you'll see what I mean once you're on the premises). This is your classic beach for good old-fashion fun. Bring plenty of beach toys and a picnic.
If you're with older kids and want to add a bit of action to your daytrip, park at Petticoat Creek (you'll have to pay a small admission fee to the park) and take the cliff trail going eastbound. Read the information section of this blog for details and to see pictures.
Frenchman's Bay Park is one of the TOP-3 day trips to the beach I suggest you consider for the Civic Holiday long weekend!