If you take a taxi or shuttle or otherwise walk in, it is about 100 yards to the Visitors Center from the gate and then about the same to the USS Midway Ceremonial Drill Hall. (That distance increases to nearly triple that once the lines are set up that weave back and forth.) The Parking Garage is adjacent to the Visitors Center. Dress warmly in winter and wear comfortable shoes all year round. You will need current ID to enter the RTC; it is possible that a person with an expired ID would be refused admittance. The Drill Hall opens at 7:00, so if you plan to walk onto the RTC arrive around that time or after. If you arrive earlier, you will be standing outside, which can get cold in the winter.
There is info on that and more in PIR Day and Liberty during PIR Weekend.
I strongly urge people to pay $2 to park at the rail station across the street. You can drive around all the traffic to get in and from there, your "hike" is probably a couple hundred yards from the gate to the hall. The walk from the station to the gate is less than 50 yards.
So, perhaps a total of less than two football fields from car to seat. Hardly a "hike"
grandson's PIR is 01/13/17 keeping an eye on the weather-we are driving up from Ohio but will take shuttle to the PIR with 2 children. Is there an area we can take them to if they get too rambunctious inside the ceremonial hall?