Flew United with 3 other adults and 7 (yes, 7) kids to Steamboat out of Boston last February. All the kids had Transpacks and carried on their helmets, boots, and electronic flight survival gear.
Little kid skis were stuffed in "normal" checked bags. We doubled up adult and junior skis in single ski bags. AND - just in case we got "that agent" - we also stuff an extra ski bag in each doubled up bag. (cus the price of an additional checked bag is MUCH cheaper than paying for an overweight bag).
When we pulled up to the terminal, we, fortunately, had curb side check in with porters. We flashed some cash, they didn't even weigh the bags, and ended up "only" charging us for the first 4 checked bags. (They took pity on the circus of kids outnumbering parents.)
1) Keep it under 50lbs. This is an immediate red flag. Weigh them at home before you leave.
2) Get boot bags and carry on the boots and helmets.
3) Tip big and curb side check in. They are less likely to freak out over snow pants in the bag than at the ticket counter. You never know when you're going to get the agent who was dumped last night and is taking it out on the world. Avoid that by hitting up the curb side check in guys.