I first went in 82 and have been almost a dozen times since. It is always a hoot and especially for the first timers. It does help however as mentioned above to do some homework and work out a plan of attack... what do you want to see or do... check the program for all the displays and workshops/forums etc. They are on all day, every day so there is plenty to choose from. Take the badges and teddy bears etc... must do advice for traveling in the US. They love that sort of thing. Explore the EAA web site fully. Join EAA.
Some of the must do's have already been mentioned, so I might repeat, but the most important is STAY THE FULL WEEK and get there early if you can.
Plenty of things for the ladies to do and you will be surprised to see how interested they become in aeroplanes (sorry: airplanes..! ) and the people there... it is just so different to what might be expected in Oz.
hints:
Comfortable pair of walking shoes required - casual summer clothes to suit - you will most likely sit on the ground from time to time, so keep that in mind.
Daytime temps will be high twenties to mid thirties C - (85-95F) summer clothes required - something light maybe for night. A light mac is good if it folds small in case of rain - usually a chance of a thunderstorm that time of year. They sell lots of them there so don't worry if you don't take one.
Take hat etc for sun protection
A backpack is a good idea
Camera of course... big lens if you have one and spare data capacity
Staying at the UWO (Uni) is good, but basic. Rooms have two single beds and the facilities are on each floor - Washrooms etc are shared, but usually clean and showers etc are private. There is often late rooms available due to cancellations.
A yellow school bus runs a regular service between the Uni and the grounds for a small charge. You will find out where the stops are on day one.
The Uni have a great Cafe where you can do b'fast, usually all you can eat for around $7 or $8. A big b'fast might save lunch?? Lots of places to eat on the grounds, but not much variety - burgers chips, and salads etc. Being at the Uni, you are close to town and there is a few good places to eat not far away. There is a tavern in the main street called "the Roxy" which has the greatest grain fed steak. (It is marked on Google Maps at 571 North Main Street) worth at least one visit. There is a bar near the Uni (short walk) by the name of "Kelly's" in Wisconsin St (near the corner of High Ave if you look on Google maps). It is a popular spot and a lot of Ozzies go there. Gets a bit like a Zoo late tho'.
At the grounds, the EAA give you a wrist band to wear for the week to show you have paid. It is plastic and will last the week ok.
Obtain a program and check the map out as well as what is on... check if there is anything of specific interest and note those times for a visit to that site.
There is lots of displays and in 4 large hangar like buildings there are many traders selling their goods - aeroplane bits to jewelry and clothing etc. You name it, it is bound to be there....
Not far from the control tower is a large white and yellow marque know as the "international tent" where all the international visitors congregate. Go there on day one and register your name for Australia. you will receive a name badge etc. There are two events during the week that involve the international visitors and you should find out when they are to be held and then go. First one is the international march where all the international visitors line up behind their country flag and march down to a building about 200m away to be welcomed by the President of the EAA or his deputy. It is a fun hour and you usually get to see all the other travellers.
The second event is an international BBQ they have at a site not far from the main gate - in the woods towards the EAA museum. It is a free feed and some beer for a few hours - but don't be late as it is very popular.
The EAA Museum is up near the highway ( Highway 41) and is a must visit. Very well put together and with lots of interesting aircraft on display. Check if your show entry gives you entry to the museum, often it does. Plan your visit during the week and maybe in the am hours. Again the yellow bus will take you there and back to the grounds.
Across the highway is an Outlet Center with about 100 shops. Range is good and prices usually well below Oz, even considering exchange rates. Some goods are better than duty free prices. There is a regular yellow bus that goes there and back from the grounds.
Don't worry too much about your return to Chicago as there is usually plenty of folk going there after the show and I have never found it hard to get a ride. It is about a 3 hr drive. Give yourself a day to do it as you don't want to have to rush at the last moment. There is always the Greyhound bus which goes from the old terminal on the north side of the airport. I usually plan to have a night in LA before heading home. Plenty to do there.
After doing the bus etc I now rent a car from ORD and keep it for the week. The rates are good and the flexibility on site is wonderful - also a trunk to put your goodies in during the day, tho parking can be some distance from the action. Enterprise I found give a good deal.
Enjoy!