The small craft channels in the 1000 Islands are well marked. Local charts
are a must whether electronic or paper or both. Sticking to the north (Cdn) side of the river will take you through a few twists and turns but nothing that you'd have to worry about. The currents can be strong but they're predictable and marked on the charts
. If you want a really easy route
go to the south side of the river and take the American shipping
channel. You'll avoid some narrow spots.
I've been on a 234' buoytender & icebreaker through the small craft channels although one Captain
put us hard aground in an area called the "Fidlers Elbow". He managed to put a 210' dent in the bottom of a 234' ship!
The biggest hazard, IMHO, are the other boaters (Jet Ski's & Houseboats) on weekends under the Ivy Lea international bridge!