Your home your rules, As for the kids yes you can tell them no but do not yell. As for the guests who don't keep an eye on their kids in the first place you should let them know to keep them in order. May be if you have gathering you should make a kids conver so their area is determined and they'll get the point to stay there (Hopyfully) but get colouring books and crayons and a few games and set up an area just for them, This way you keep control and wouldn't look *****y
But on top of that, these should be rules that they already know. Shame on their parents for not teaching them. If your polite request isn't polite enough for their tastes, then they can take up the issue with their parents.