At home I usually just leave DS in his vest or with cheapie trackies on as well. I put a towel in his lap to help catch the fall out. Still, it's a messy business but I'm ok with it.
However i find it a bit tricky when out as a change of clothes isn't always practical. Today, for example, my DS ended up with red stained cuffs from his tomato slices. And it was a white top too (yes I suppose i am an idiot to let him wear white whilst eating!)
I'm just wondering what everyone else does for damage limitation when out & about?