BB will take ~ 4 (four) to 5 hours (check after 4). And do them 2-2-1 (if you foil at all; I don't but the hours remain the same ie about 4-5 hr). Do 3-2-1 method for spares.
Chicken, well I wouldn't do it at 250. It'll take 4-5 hr and you may very well want to add it to your charcoal pile when you're done. Best done at 350 for an hour or less(probably a LOT less time than an hour). Great skin pleasantly brown and meat is tender/juicy.
Here's a link for what it seems you're trying to do.
http://tvwbb.com/showthread.php?56232-Simple-smoked-whole-chicken-on-the-wsm although this was for a whole bird, not pieces.
You can also start your ribs at that temp (350) alongside the chicken and then start lowering the temps (after the first 40-45 min) for the remaining 3 hours or so for your ribs. Be careful of hot spots wiith the temp at the level for the ribs (normal smoking has them much further away (and somewhat protected by the bowl) from the heat.
When I broil thighs (in the oven, I know it's sacrilege---but its
quick ), it's like 25 minutes for thighs.
Personally I'd do the ribs first at 250, take em off (and
then foil to maintain their heat) and bump the temps up to 350 for the chicken. They'll only take 25 min or so (from your own experience you know how long) and the ribs will still be wayyyy hot.