If you can post pictures, that would help a lot... the location of serial numbers-- if present at all-- can vary from one builder to another. Many put the serial number on the stem (floor of the canoe, up near the bow and/or stern)... sometimes it's on a rib... sometimes on a part of the canoe that can more easily go missing over the years. Sometimes it's on a metal plate and sometimes the numbers are impressed into the wood. Fairly complete records exist for only three of the old canoe companies, but with a few others, a varying degree of information may be determined from the serial number. Sometimes the lack of a serial number helps narrow down the builder...
Pictures say a lot... scroll down to the box below the one you type into and find "manage attachments"... click on that and you'll get a browse box that'll let you find pictures in your computer.
If you'd like to poke around the Dragonfly canoe I.D. site, you might find an answer.
http://dragonflycanoe.com/id/index.html
Scroll down on the left to the canoe builder you think may have been responsible for your canoe, and click on that. Check out "Old Town", and perhaps a few of the Wisconsin canoes, such as "Thompson" and "Shell Lake".
You can use the "search" function above to find old posts and can narrow the number of things you'd have to read through by narrowing the search parameters-- i.e. "Shell Lake serial number" etc....
Cool project--- a great thing to do for (and with) your kids!
Welcome to the Forums!
Kathy