welcome to MN! I sail Mille Lacs & Superior. Have sailed Lake Pepin a few times, along with Minnetonka. Lake Pepin would be just fine for your cat. Lots of speedboat traffic & barges...but a nice place to spend some time on the water
. Never been on the St Croix, but when I drive that way I don't see many sailboats. Perhaps the width & current
are not favorable? Why not try Mille Lacs? 18 miles wide & 27 miles long - lots of good sailing weather
& varied conditions. PM me for more info.