If your close to boom island then I would just go over to twin lakes in Robbinsdale. I love about halfway between them in north and usually go to twin lakes when I just need water to test, winterize, etc. it’s rarely busy. Just go West on 81/Broadway and it’s on the right side before you get to 100.
The launch is on to a small no wake lake. Go under the bridge and it goes to a bit bigger lake. If you go across the second lake there is a longer windy channel that connects to a pretty good size lake. It’s much bigger then you’d expect and pretty well hidden.