My Little Pony LIV:E Long and Pony!

[Tiki Snakes]

So, Colgate/Minuette is both Dentist/Timepony who saved Equestria in the distant past?

Princess Platinum, it all makes sense now! :<

Well, said background pony does have two main interpretations; Colgate the Dental-Pony or Romana the Timelord Pony.
It does, indeed, make perfect sense.

... what, so messed up teeth make Discord stronger? Is he in league with the cavity creeps or something?

Straightening your teeth via dentistry is an imposition of order upon natural disorder. In this case, it would almost be like a ritual thing, taking the spirit of Order into yourself as protection against Discord.

Following that logic, imposing Pony-control on things could act as a way of weakening Discord, insulating Ponyfolk and their land from his predations.
Say, by severing the natural cycles of the weather and putting Ponies in active control of it instead...

On the subject of the Marriage of Pinkie-Pie;
As I have no idea of the context, or themes you're trying to evoke, I can't really suggest an alternative event as such.
However, I would suggest sticking to existing characters for the possibles if nothing else. That doesn't leave you with many colts to pick between, whether that's a problem or not is your call as you are the one who's going to be writing this. If you aren't bothered by who she's paired with because the wedding is what's important rather than who it's to, I would suggest instead going with whatever the most widely supported Pinkie-Ship is.