Once you kill all 10 dragons that's it? Why did you choose that? Killing dragons is the most fun part of the game. They're incredibly fun to try and defeat. So why not make them spawn a higher lvl after about 5 hours of gameplay(this number can vary if it's too low or high). Just change what they drop the second time to random. This way you can fix the gold exploit and people will be able to have enough dragon bones, webs, and scales to craft gear for their party.
Dragons aren't mushrooms. They are apex predators, which means they are also few in number and control a large territory as a solitary creature.
Besides, you're going around killing off all their offspring, so how do you expect them to respawn so quickly?
It would diminish their significance in the game if they were to respawn at all.
Silly idea. Put it out of your mind. This is not Skyrim.