Well, when coming up with a date idea you want to try for a couple of things:
First of all, what you don't want to do is make her think that this date activity is being done for the sake of her. You want her to think that it's being done because you want to do it, and that she's just along for the ride. If you can make her believe that you're feeding the ducks because you want to feed these ducks and aren't doing it for the sake of having a date activity with her, then go for it.
Secondly, and perhaps more obviously, the date activity must be fun for her. Personally I do not think feeding the ducks (with maybe a picnic thrown in) is all that fun. It will probably just devolve into a date based around conversation and devoid of any action... and it's best to avoid those. It's boring and stressful for both parties to continuously keep up conversation. When one-on-one it's best to aim for some sort of action date. Go play some pool or something. Even a movie date would be better.