I think I may have to just pick some out and send them off after the dragon. I can then work out the challenges to face them. It's not like I have my heart set on the dragon fight going a certain way. Just because it's a novel doesn't mean it can't work that way.
I may even just have to choose what level they are. Other works, I've picked it out by deciding what is the max level of spell I need a character to cast, but I haven't got that picked out here, either.
All the more in that this story, there is plenty of time for the characters to level up. Gives you quite a bit of leeway -- especially in that there will be a war going on to give them plenty of chances.