If Dad is a meat-eater, you might consider Na'Brasa Brazilian Steakhouse in Horsham. They have a Sunday brunch with rodizio-style sausages and breakfast meats, as well as a standard brunch buffet. No outdoor seating though.
Funny you should mention it, but I did. That's a possibility. And while I was on the website, I stumbled onto their monthly Thursday night BBQ events. Those look awesome. We may just move the actual celebration of Fathers' Day to one of those dates!