Re: flying with a 3mo old?
Hopefully, they won't give you trouble about wearing baby through security. If they did ask me to remove my baby before going through security, I would probably just ask a polite question about it, but I wouldn't cause a scene if they insisted on it. I think is is important/good to know what the official policy seems to say so that at least you stand a chance :-) Of course, be prepared for either way!
Good advice on slip-on shoes, empty pockets, breastfeeding during take off and landing!
If the airline offers curbside check-in, that makes life a lot easier, too!