I can understand your dissapointment, my group had planned around the ride opening on the 25th. However, we all watched the boards, the announcements, etc and when the change was announced to the 26th we immediately grabbed a room (at an extra $150 a night for a room that up until Monday ran $89.00 per night).
Friends from Denver (also coming out for the re-opening of PotC) were locked into plane tickets to depart on the 26th at 8:00 a.m. So, while I was (jokingly) asked.."common, Kim..you know a LOT of people who work for the mouse" it still didn't matter. (Like I had THAT kind of knowledge and influence...yup and elephants fly..oh wait..Dumbo..well you know what I mean.) And, while there is a small SMALL chance of a soft opening on the 25th, it would be better not to get your hopes up. But you could wait outside the ride, explain to the CM and see if you can get a "hint" if there might be a soft opening later that day.
Perhaps if it was a Make-A-Wish event and time was of the essence they might let you through early...but I would suggest if you can, postpone the trip for a few more days if possible. If not, then be honest with your son and tell him it's not open and sometimes we all have diappointments. Then try to make it the best trip you can anyways.
But, honestly, we don't always get what we want do we... I mean if we did.. then when I look back over my shoulder at my newly re-done PotC style bedroom..there would be a certain Captain Sparrow lying on it..motioning me to come on over...
Edit: On a very serious note: I had passes for the original PotC Red Carpet and Film Event. A Friend of mine worked on the film and was able to get my sister and I passes to get into the screening. Unfortunately, the morning of the day we were supposed to head down to the park, our Dad was diagnosed with terminal Male Breast Cancer. Needless to say, we didn't go. We immediately called our friend, explained the situation and told him to give our passes to someone who really would love to be there, but otherwise wouldn't be able to go. And while we missed a once in a lifetime event..it was nothing compared to those last six weeks we got to spend with Dad. No regrets...none whatsoever.
This time, he is still trying not only to get passes for himself, but for us as well. As of this minute, it is not looking good for any of us. But you know what, it's ok. It has a whole new perspective this time around. If we get them great..if not..that's ok too, cause we are going to be with friends in the park.
So, if the ride is closed, your son will survive. He is four. There will be enough pirate merchandise to spoil him rotten with. But, like I did say..you may want to start preparing him now for life. It does happen and the best layed plans...can be turned around without a moments notice. Hope you still manage to have a good time at the park. He's four, he's gonna have a great time PotC or not!