The joy of a panel is you can make it however you would like. Do you want it to have many boarders? Or to you want it no big deal here's a quilt?
Just cut them apart on that dotted line you mentioned and you're off and running. When purchased off the bolt it would be one "panel" for "x" dollars, and you would buy one or however many you wanted.
Another thought you said you have three sons, but if one or two isn't into Thomas you could make one quilt and two curtains. Or one quilt with a matching front and back (that only works if you were planning a not to quilt on the lines).
It's so nice that your neighbor thought of you! Enjoy the quick answer. :D