Your game has to be very keep away and turnip intensive to even the tables vs. Ganondorf.
I sorta play this match like the way I would against a Marth. However, fsmash, usmash, up+B, and even utilt become valuable tools to outprioritize Ganon's aerial game. Fsmash is disjointed and hits in the spot where Ganon loves to be - above and in front of Peach. Usmash and Up+B from shield cannot be overlooked when Ganon is varying his jumps into aerials. As for utilt... yeah, even that works. If you suspect stomps, SH an aerial or Up+B.
Recovery can be a bit tough, as Ganon can actually edge guard Peach and chase down her floating if there aren't significant platforms involved. Floating high is ok, but Ganon is still capable of rushing you down before you land, unless you're on some Battlefield-type stage that gives you platforms to work with. Aiming under is also ok, but his spike and edgehog are a cause for concern. Coming from below means you need enough jump left to Up+B on the stage safely should he attempt an edgehog. To come in at an even level with the stage, use Toad to turn Peach around before attempting to fly back. Bair is by far the toughest aerial for Ganon to hit Peach out of.
As for edgeguarding Ganon, turnip spam off the edge. Grab and fthrow him when possible. Dair combos are excellent when he attempts to sweet spot the edge. If he DI's behind you, you can simple FC and dsmash him back out. If he stays in front, you can immediately nair him, or FC and fthrow him. If he can come in high, none of this applies. You have to chase him down with running dsmash or a grab to get him back out. He can be tricky coming in high, so don't do anything unless you his landing point figured out, because losing killing edgeguarding opportinities sucks with Peach.