I think this ties directly into What happens when you target a "magical effect" with Dispel Magic?, because the rule is "roll on the Wild Magic Surge table to create a random magical effect", emphasis added. It's possible that these can be dispelled.
Interestingly, only the blue skin effect notes that remove curse can be used.
If a player isn't finding the height/age changes to be fun (and... if you're 12, being dropped to 3 years old is only another set of unlucky rolls away), I think I'd allow remove curse or comparable magic to fix it. Or, if that seems too easy, it could be a plot hook for finding something that will work. (Perhaps researching a spell or a medicinal cure, but think about all those movies where the main character changes age — the solution is usually in character growth of some sort. I wouldn't force this on a player, but if they were down with it, having the character learn to "act his or her age" in some way might cause them to return to their true age — wiser and better for the experience.)
Although there is a list of wild surge possibilities provided, I think it's pretty clear that the flavor isn't intended to be "one of these known possible consequences occurs" — it's mean to be "something bizarre and completely unique happens". So it stands to reason that there are no known formulas for undoing some of the effects. In an open role playing game, that can be awesome, because discovering the solution is a strong motivator. On the other hand, if you are deep into an adventure where an arbitrary diversion into solving your problem doesn't make sense, I'd ask the DM to help find a less-disruptive way out.