Yep, get some plain black tennis shoes if you need to wear tennis shoes with skirts (Sketchers makes some great stuff). Or, throw your fancy shoes in an oversized purse and change when you get where you're going.
Woman over 30 should only wear sneakers to the gym or some sort of athletic activity. Definitely not with a leopard print skirt. And I think leopard print only looks good on a leopard, too old too gotty.
I wouldn't do sneakers and a skirt unless you are trying to pull a sporty tennis player look. So no, I wouldn't do it with leopard print. Not that I really approve of leopard print at all.
I recommend you either save the skirt for another day, or wear other comfortable shoes. If you really want to wear the skirt and have no comfortable shoes you can walk there in, maybe bring a pair and switch them for the event.
Depends where you are walking, and with whom. In the city, I would never wear sneakers with a skirt (except maybe with a jean skirt). On a country road, walking alone, sure, what the heck. But, as a general matter, sneakers and skirts are not a great combination. And I'm guessing you know that already. :)