I am coming off allergies and no sleep so forgive me if I am more ADD or incoherent than usual.
http://www.mouseplanet.com/potties/
That is a full list of Disneyland bathrooms. It includes number of HCA stalls, high or low urinals, flush types, faucet types, type of changing tables, mirrors, a picture of the entrance, and comments. There is a page listing where manual flush toilets are located, the items available at the Baby Center and a bit about the Nurses Station.
All rides at Disneyland allow a guest to wheel onto the ride such as the Train or roll up to the ride vehicle to board. Some like Alice in Wonderland use the exit which is a short walk and the guest can roll the
ECV or Wheelchair up to the ride vehicle.
If you plan to drive then bring your handicapped placard from your homes state. Since you might want to have your son walk through an exit, which is a short walk to the ride vehicle, then you would need a GAC at DLR. Most Fantasyland rides are pre ADA and there is no room to make the ride lines wheelchair accessible.
The train is wheechair/ECV accessible except for Main Street Station where you have to walk down lots of steps. I did not like sitting in the bench seat where the wheelchairs are put. that is because the back is so low that I get a phobia attack because I feel like I am going to fall out.
DCA is being remodelled for the next few years. It is very disabled friendly and has more lines where the disabled have to stand in the main line for a while before being specially loaded.
Disneyland does have a baby swapping pass (whatever it is called) where everyone rides but one person who child sits then that person and one or two persons then rides through a short line.
There is plenty to do at DLR such as the gentle steamboat, the train, small world and shows. Disney goes out of its way to make sure that disabled guests can access rides somehow. The except is Peter Pan which is at one point is 10 or more feet above ground. For at least 20 years this rides was off limits to disabled guests in that if the ride E-stopped and an evac was required then it would be very dangerous for the disabled guest to be safely brought to the ground.
If you have questions about DLR and the southland ask but as you see I aint always clear headed, wow what a run on sentence.