Hey Prospector16, glad you're doing this! I know we talked about it months back but my heart led me back to making static maps. (Publishing a new one tomorrow actually.) Using Google Maps is a practical choice for a trip planning map, and the API is great.
Toporama is a great resource, but I've never tried importing. It's likely a formatting issue. Are your CSV points in lat/long? Decimal degrees may be best to avoid formatting issues with DMS.
I would just download Toporama's data and bring it in to whatever viewer you're working with. If you don't have ArcMap, QGIS is a free alternative. Download all the layers you want from Toporama as a geodatabase, then bring that into ArcMap or QGIS. You can convert formats in here too so that they're Google Maps-compatible.
More importantly, are you familiar with LIO (Land Information Ontario)? Tons of good public info here. Most pertinent for you is the Ontario Trail Network. Search that here, hit the download button, and fill in your info to receive the download link.
https://www.javacoeapp.lrc.gov.on.ca/ge ... /main.homeIf you need any advice let me know.