I've had kids like that too. Honestly, and people might think I'm mean, but I'd only encourage them for a couple minutes. If they don't want to even try, they can sit there. They'll do it eventually if they're not getting attention for NOT doing it. If the shoe area is near where you play, just go on your way. As soon as you see one of them take off shoes or at least make a clear effort, bring out the brass bands, throw a parade and make it a really big deal! Then you've moved to giving attention to positive behaviours instead of negative. That's what worked with a few kids I've had over the years.