You must think that a surviving Bonaparte on Elba would have become something of a celebrity. He would eventually become a figure of longing for the French people to recover the ideals of the Revolution without the excesses of him. Napoleon's death in 1827 should shock the spirits enough for a July Revolution to occur in 1830 that Napoleon II can take.
You touch on an important topic -- the Napoleonic myth did indeed exist, and Napoleon was probably more popular after his death than in life (while his early military and political successes were much appreciated, by 1815 France had lost nearly an entire generation of men, much of the French peasantry resented mass-conscription, and the failure of France to even gain success in Spain when only a decade and a half ago, the French had little problem fighting Spain). Nevertheless, what some scholars have indeed pointed out is that while the Napoleonic myth gained popularity in the aftermath of Napoleon's death, it did
not channel into Bonapartist -- e.g. a desire to enable the Bonapartes to gain hereditary control over France -- sentiment. In fact, it was seen as so unthreatening that even the
July Monarchy patronized Napoleon's memory.
Napoleon III, IMO, came to power less because people connected him with his uncle, and more because Napoleon was able to position himself as a moderate in the midst of the political instability of the Second Republic, and appealed both to the peasantry and working class (who saw in him a champion for their interests w/o going "radical") and to the conservative right, who felt he could be controlled. That set of circumstances was not present in 1830, when the Revolution was primarily organized by moderate monarchists.
Anyway, before we get into the details, let's first imagine the big picture: Napoleon II takes power comfortably enough, what happens next? How do the European powers react? What can Napoleon II do to appease them? What do you think his policies would be? Etc
I don't think Europe, including France, has the ability to stomach another set of Revolutionary wars. Nor do I think Napoleon II (who has spent his entire life in St. Helena) is going to have the skill to organize such a war. Europe will likely be alarmed, but not so alarmed that they will go to war with France. I think in this case he will actually be heavily reliant on his advisors; he'll be 18-19 years old, after all. I don't think he will marry a member of the House of Bourbon -- remember that each revolution had been implicitly founded on rejecting the previous one, so it would be odd for him to marry into the previous ruling family. If he's smart, I suspect he will try to acclimate to the Concert of Europe and possibly marry into the Austrian Imperial family.