My family does BB every trip, because my son (now 5) loves the place, and has since he was 2. so I'll breakdown the lines for everything based on my recollections (3 trips in late August, 2 in October, 1 in November).
Downhill Double Dipper is the slowest line in the place, because it loads incredibly slow. Do that first thing if you want to do it. The line is deceiving, it will be physically and numerically short, but take a long long time.
Summitt Plummet will have a long line except first thing in the morning, but it is worth it. Get up the courage and go!
Slush Gusher is a good alternative to S-P if S-P's line is long. SG is usually not too bad a line, and it is good slide.
Runoff Rapids single tube (enclosed slide) line can get to be 10-15 minutes after the climb, plus 5-10 waiting for a tube before you start the climb, but double always moves quick, so find a buddy or a family member to go with you.
Teamboat Springs, the family raft ride, is my favorite. Line is never too long (5-10 minutes tops) and you don't have to carry your tube up with you like you do on Runoff Rapids or the family rides at TL.
Snow Stomers and Toboggan Runners (don't know if I got that name right) generally don't have long lines (10 minutes or so) and can be done anytime.
The Chairlift can have a very long line, but you should do it once at least. We do it more often because of our son -- too many times up the steps can wreak havoc with a 5-year-old's mood, and we can't carry him anymore! The view from the lift is great, and early in the day, the line is usually short. If you want to use it later and the kids are old enough, use the single riders line on the lift. Since the chairs seat 3, they need a single fairly often.
One other recommendation is where to sit. My family and I always head for the chairs near Tyke's Peak, which is the kid's area for toddlers. There are several areas that are shaded by wooden structures and we grab chairs on the edge of one of those, so we can move in and out of the sun as desired. It's a little off the beaten path, plus there are very few teenagers and other rambunctious folks around, so you can actually rest there should you desire to do so.
