Jeni:
I have 3 kids, ages 5, 2, and 4 months, and I have been flying 4 1/2 hr trips with them (CA to MI), every 6 months, since the oldest was 6 weeks old! Sometimes by myself (without my husband! altho not with all three have I yet done it solo)
Try resale shops in your MIL area to get the baby stuff you will need. Carseat, booster, stroller?, and pack n play (crib). Does your MIL have any friends you can borrow/buy from? My mom's friends are grandmothers too, lots of them have extra stuff to loan. It is smart to think ahead though, as you are!! Smart smart.
As for the plane, I suggest non stop and leaving first flight, early in the am...if possible. 12-18 months is the most challenging age, but you can do it. Assume that Olivia will not sleep at all on the flight (mine never did..even if I gave them benadryl). She will probably be crabby at some point. They are just so excited.
See if you can rent a portable DVD player if your airport has the service. I rented mine from
www.inmotionpictures.com I think...$20 including the movie...or you can buy one. If you think you are going to be traveling a lot with kids for a long time to come, I suggest buying one if at all possible. Maybe save up or ask for $ as gifts til you can afford it. Really it is the best solution I have found in the 5 years I have been doing it.
Otherwise, on the flite...LOTS of food that she likes in tiny pieces...like raisins if she can have them...bits of fruit, healthy snacks, things that take a long time to eat (teething biscuits). Things you don't normally let her have, or ever will again. Think "bribery". Sugarless suckers or something to suck on for descent and ascent, to protect her ears (I also used full strength juice, held back in a special cup, to bribe them back into their carseats for descent..I normally dilute juice heavily or didn't give it at all til they were older so this was a one time only treat) LOTS of books. Toys she has never seen before (I go to Party City and get some party favors, they are cheap).
If you go with your husband, one of you boards alone, during preboard and gets the carseat set up, one of you waits in the gate area with Olivia and lets her work off more energy, then boards at the last minute.
Fellow passengers will be sympathetic and in general helpful if they see you are trying to do your best with an uncooperative child...so don't worry about that type of thing too much. You'll never see them again anyway!
Sit in the bulk head if you can for the extra leg room. If not, get the last row near the bathrooms. More room to let her play, more activity for her to watch.
Lots of airlines now have online boarding passes you can print from home before you leave. Helps save time.
Changing table...lots of the planes have them in the rest rooms...face the toilet, it looks like a giant fold down table in front of you over the toilet. If not, change her on the toilet lid. Bring an extra (lightweight) outfit for her in case something goes wrong.
As far as what to bring in the suitcases...pack light for her, you can rewash clothes at your MIL. I always bring too many clothes for the kids! Bring her favorite blanket/stuffed toy with you of course.
Good Luck & let me know if you have anymore questions. It will be fine....you can do anything for 4 hrs right?
Jen