(The starting point on public map and link isn't exactly our home.)
The trip is entirely on bicycle trails or quiet streets. Note the crossover Stone Arch and then down to Nicollet island then taking the short gravel trails to Boom Island.
There's an alternative route that takes the bicycle trail on the "east" side of the river. The trick there is that there's an illegal but now heavily used path under 35 W by the rail yards that connects Stone Arch bridge to the UMN river path:
Sooner or later that use path will get either closed/enforced or made legal, but for now it's in a happy limbo state.
Update: on the return trip a tired family member and ominous storm clouds required this shortcut to the above 35 W underpass route:
This was a surprisingly quite and pleasant route -- but 3rd Ave NE bike path is almost unrideable. Just take the quiet street.