H.D.
Bring antibacterial wipes and wipe off everything you think she'll touch...arm rests, tray tables, window shades,etc...she may find those things entertaining to play with because they are new to her. My son used to love to lift and lower the window shade and push the light button on and off. Taking plenty of snacks and maybe a new toy or book that she hasn't seen before will occupy her for a while also. To manage all the gear...use a backpack for your diaper bag that way you'll have both hands free to push the stroller. You may be able to balance the car seat on the storage basket on the bottom of the stroller and support the top of it with one hand while you push the stroller with the other. If you don't think she'll sit still in it you may just be wasting your time and efforts trying to lug it along. It sounds like you may be better off just checking it or getting one with your rental car if you are doing that. Don't worry...people are usually helpful if they see you struggling especially at security. The yogurt must be left out for inspection and they may make you pitch it and buy new once through security. Make sure she eats or sips on something on the way up and on the way down to keep her ears equalized. This has worked EVERY time for my boys. If your baby watches movies you may want to bring a portable DVD player for her to watch too. Good luck!