And don't bring any packs - just tie your sneakers to the back of your harness.
This I gotta disagree with. A tiny pack with 1) windbreaker 2) water & snacks can make all the difference in comfort on a 7 pitch climb. A tiny headlamp should live with you IMO... nothing more embarrassing then getting caught without one... If you can't lead 5.7 slab with an 8 pound pack on... well... you shouldn't be leading... Seen quite a few dehydrated hungry chilly people 5 pitches up with thier backpacks stashed at the bottom. It's slab climbing... a tiny backpack won't slow you down.
And a carabiner through the bottom lace of the shoes will ensure your shoes are still with you at the top and is quicker than tying them to your harness
With enough experience & technique a 3 person party can climb Whitehorse faster than the average 2 person party. What slows people down when belaying 2 seconds is not being able to take in slack fast enough on both ropes through a high friction belay device like a Reverso (I love the Trango Cinch for this). If I'm climbing with two people who know how to second slab (i.e. climb fast) I prefer to lead on 1 rope and belay them up individually... this is only faster IF they climb slab fast. I.E. stand up and walk up all the 5.3-5.4 bits... they should only climb slow at the cruxes... Even beginners can climb slab fast if instructed to stand up and climb vrs. slowly crawling their way up 5.3. I'll routinely be behind 2 person recreational parties with 2-3 new clients and still have to wait.
Also move rope efficiently... have your seconds help out at the anchor to quickly re-organize. Slow parties usually lose the most time at transitions (belays) exchanging gear, re-stacking the rope, etc. If the route doesn't traverse have the 1st second clean most the gear. You can be pretty much re-organized and ready to leave the belay by the time the 3rd climber arrives, even if he is only 30 feet behind the 2nd climber.
"Alpine Climbing" by Mark Houston has some great speed tips that carry over when to moving efficiently on multi-pitch trad. Also a guided day with a qualified guide focused on improving your efficiency leading multi-pitch routes can open your eyes to some ways to save time.