Are you positive that everyone eats pork? Pulled pork is very popular but you have to be sure everyone eats it. And PB&J - you have to be sure that nobody has a peanut allergy. But if these are all good friends and family, you probably know about most, if not all, of them. The sandwiches can be a little messy to eat, and PB&J can be as well - so be sure you have people on hand to help you by picking up plates and so on.
Are you looking for pulled pork recipes, or recipes for other options? I couldn't tell from your question but since you say you don't like anything but chicken, are you looking for a chicken recipe you can enjoy, or just trying to do something for your guests? I just catered a big party for about 30 people so I went through a bunch of recipe options. Everything I make can be done ahead of time if that helps. How many people are you expecting? You definitely want things that can keep over time so people can serve themselves. If you're going to be running party games or kiddy activities, you want something low maintenance. I do my own chicken nuggets that are healthier and easy to do ahead.
I would cut the sandwiches in quarters and take the crusts off the bread - you know how kids are! Or you can get one of those bread cutters (like a giant cookie cutter) to make them in a fun shape.
You could also do cupcakes instead of a cake - 4 year olds aren't so good with forks. People put them on those cupcake stands or just on a platter. We did a kids' party with cupcakes arranged in a wavy line like a caterpillar, with different candies as those caterpillar "bumps" and shoestring licorice as the legs and antennas. For 4 year olds, I would do the mini-cupcakes and those who are hungry can have more than 1. Less waste.