Ethiopian Airlines allows 2 checked bags per passenger. Since my mom, Abigail, and I all have tickets, we each get to check 2 bags (as well as have a rolling carry on each, and a "personal item" ie-backpack.) I will use the 3 totes of humanitarian aid as part of my checked bag allowance, and I will also check 3 rolling suitcases.
On Ethiopian Airlines, extra checked bags are $135 each. Thankfully, I will not go over my checked bag allowance. Overweight bags are figured at a percentage of your ticket price, I think. But again, I refuse to go over weight, and will par down my packing list if my bags are over at all. I am flying out of Dulles, so I don't know what restrictions might apply if you are making a connecting flight to Dulles/NYC.
Navigating the Airport
When we are dropped off at the airport, my plan is to load the totes, one suitcase, and several (all?) of our rolling carry ons onto a cart. My mom and I will each pull a rolling suitcase and Abigail will pull either her rolling carry on or one of our rolling carry ons. We will each also carry our own backpack/purse. I think since we will be dropped off right at the departures area, we can manage to get to the ticket counter without difficulty.
On the return trip, we will have only the rolling suitcases and carry ons to manage. Again, I plan to use the cart for as much as possible, and with my mom and Abigail there to help, I think we can manage it all (Anna will most likely be in a sling/wrap which will free both of my hands for luggage.)
Getting to/from the Airport
I plan to use my Saturn Vue to drive to and from the airport. It will be tight (especially on the way to the airport) but I figure that if I have to hold a carry on in my lap and have a suitcase take up most of my leg room during the 2 hour drive, that is really not that bad. John will drive us to the airport, so that will mean we have 3 adults and one car seat on the way to the airport. That will still allow us room in the backseat for bags, as well as plenty of room in the back for totes and bags. I hope. Seriously thinking about measuring everything out:)
On the way home from DC, we will have 3 adults and 2 car seats. This means that everything must fit into the back. However, I anticipate less luggage on the way home, and plan to reduce the number of rolling carry ons we have by packing them inside my regular suitcases for the flight home (the way I store them when they are not in use.) I have done this on other flights and found it really helpful. I don't plan to bring anything home other than our clothes/shoes, books/toys, and souvenirs. (Food, toiletries, and anything else that I have at home will be left in Ethiopia.)
If we had a minivan or a friend with a minivan, I would have no worries at all:)