General tip regarding the Grand Canyon: Even in February, as soon as you get your dates pinned down, try to get a reservation if you are planning to stay in the park itself. Even in winter months, they book quickly. If you strike out the first time, keep trying back, as you never know when they will get a last minute cancellation. (This is a song we sing on these forums all the time; national park hotels book fast and furious!)
Another tip: Bring clothes that you can layer. You're going to be crossing several different climates at that time of the year.
Third tip: Allow an extra day for travel in case you get stuck somewhere. Better to have to stay in Tusayan if you get to the GC before your reservation than to get there a day late and find out they made you pay for it anyway. ALWAYS CALL if you have a reservation somewhere and need to delay/cancel it, or you may be liable for the night's fee.
Donna