First please don't give a tranquilizer!!! Okay, since I don't have a B yet I can give my expereince with just flying with my boxer who is a world class traveler from short flights to international flights.
I'm guessing that they have never been on a plane before? I'm also going to ask with what airline you are flying? Okay those out of the way. Airlines take very good care of pets on flights, and though you do hear the "horror" stories they are actually VERY rare nowadays. Next is for something to help calm them I'd suggest Rescue Rememdy. My cat is also a traveler but hates cat size carriers and giving her the rescue remedy helped her relax and not be as stressed.
Next best thing is to make sure they are very comfortable in thier crates for an extended amount of time. Moving on, when you get to the airport you will have to take them out of the crate so it can be inspected. Make sure that they have thier collars with your info on it. My suggestion is to always have your cell phone number on collar tags (I only put those on tags because you will pretty much always have your cell phone on you).
As for stressed well, there is no denying stress, best way to manage that is stay calm yourself, you can put toys in the crate with them. Also you can take the crate bowls in there with frozen water so they will have water. If it is going to be really cold where you leave and where you go and they will tolerate it you can put a sweater on them.
I think I covered it all, please ask if you have anymore questions, I have travel by air many times with my pets