I've kept my pet Pekin drake as an only duck for three years now (and have just finally been able to get him some friends.) Casper was raised indoors, is totally imprinted, has been trained to use a leash and harness, and has been taken on road trips and to public occasions with me, so I guess my situation is very similar to what you're planning. I tried using diapers for a while but I just can't get them to work for me so I gave up. I just keep him outside or on a towel when he's inside.
So here's the deal with the 'aggressiveness'. Casper has never showed any aggressive tendencies in his life and I wouldn't expect that from an imprinted duck. But -and this is an issue that I deal with every day- he pinches. It's not because he's trying to attack me, it's because I am, as Mike Winters eloquently put it, his "love interest." Male ducks are all about mating. My drake just loves me so much that he can't contain himself and he absolutely thinks of me as a mate. He never stops really, it just get's worse in the spring! Haha. I've taught him not to do it, which was pretty hard, but I still have to wear boots when I play with him because the consequence of a slip-up in his training can be incredibly painful. He's still my sweet pet duck, it's just a problem that I have to always keep in mind.
When I take him out in public the pinching can be a problem. If he is nervous, and much of the time he will be, he wont really be 'in the mood' for that sort of thing. If he meets somebody that he really likes he can get a bit pinchy though, and I have to keep my hand over his bill just in case. Generally, pinching is the one thing stopping a great duck from doing the things you're thinking of doing with your duck, like meeting lots of kids. There's just always that small chance that he'll pinch somebody's lip if I don't have my hand on his nose so I don't risk it. I mean, he hasn't actually pinched anybody besides me and a few family members that he's very close to. It's just that I worry about it.
I would say that you should absolutely get a female if you want to take her to public places without having to worry about all of that stuff. For so many reasons, just pay the extra 60 bucks or whatever it takes to get a girl. She would be noisier but would probably make a great duck for your purposes. I have two girls that I'm raising right now that I got from Metzer Farms and they're great, so I would very much recommend that hatchery. I'd also say that you should go with a smaller strain of Pekin because they tend to have a very friendly personality, though my new Blue Swedish and Buff Orpington girls are proving to be pretty great too. The Swede is incredibly calm and mellow so perhaps that would be a good choice for you.
Just make sure that you know what you're getting into. An only duck requires so much extra attention and affection. Also, the mess is never-ending and enormous. It's kind of like having a puppy that never grows up. Perennially adorable yes -but they will never be potty trained or grow out of that needy phase. You might consider getting a handful of ducks to keep outside and teaching a few to be taken to see people. It would probably be less work that way. And Oh Man! Don't underestimate the poop.
