Obviously it's just MHO but I think you are cheating yourselves out of something based on fear instead of facts.
Planning does not equal something negative. It means needing to adept to a new planning for those that didn't plan this way before. Yet, it can be done very well. The
MDE app is a great tool in that, with all kinds of live info like wait times, being able to make and alter reservations, find caracters and lots of other things. That app makes planning lots easier, you've got all standy by times at the palm of your hand, for all parks.
Than factor in the scheduled show times, of which there are also many. By now we know a lot about the FP+ trial and how to "trigger" and invita (stay at certain resorts, tickets bought and linked beforehand etc). That gives even more options in one. Thats even without adding in "double dipping" where you can also still use regular FP system.
Just to give an example of a first day;
enter park and head to GR to discuss needs, questions about new system etc. Be OPEN to new things and learning. CM's are also learning but have lots more experience than you with the system, and it adds on each and every day. They can have all kinds of tips and tricks that can help you out a lot, but it can take being open to them. Lets say it's found
DAS works best for son.
Now you move on to the park-experience. Grab a first DAS return time
-meantime enjoy a show that is having scheduled times and thus predictable, plannable etc. Huge range of options, whether from options like the Muppet show that run at set times, to a Beauty and the Beast, backlot tour etc.etc.
- ride DAS ride
- get new DAS time
- ride a FP+ ride
- see parade
- eat something
- ride DAS ride
- get another return time
- you use your app and found a ride with managable wait time, thus hit that
- another scheduled time option
- ride DAS return time
this is even with minimal usage of the app, little perfectioning FP+ and leaving out the regular FP.
Assuming is a recipy for trouble. No assumptions it THUS will not work because there are 2 of you that need to stay with son and son can't come along to pick up return time. Instead discuss this question/worry when hitting GR.
One of the many issues I'm dealing with is a max. sitting stamina of 30 minutes, quite limiting as a wheelchair user. First aid is great, but can't offer minimal I need for downtime, so back to the room it is. I travel solo and crowded lines are out due to such risks it can be life threatening. I have no DAS (been at WDW for a few weeks now). Had I gone in too focussed on "allmighty DAS", sure I would've ended up with one. But; it does not work best for my needs, amongst others because of that combination of max 30 minutes and solo. I discussed this at GR, nothing more or less but "this is what is bugging me to work with, got any tips or tricks for me about that". Already got some great options and info from there, but best tweaking was done because I basically literally told cm "it's not upto me to decide give me accomodation A or B, I can communicate my needs very well but will have less knowledge about my options than you guys do". No DAS for me, but an accomodation that works better and suits my needs. (yet by many only get read as "see, an adult not accomodated, shame, bad system)
Within it being an ability, being reasonable and workable it still does come down to accomodating individuals, not a one-size-fits-all. Are there kinks? Sure, what new system wouldn't when so many different issues are involved, with so many employees and also so many expectations which include those fed off of improper accomodating done in the past. But; it's a learning curb. Yes it does require certain planning. Yes it's different. But it's not thus a negative new era.
Dont undersell yourself or son by basing decisions on fear but give it an honest try. Read up on what has worked for others, consider how you can translate that to your families situation, and discuss worries and fears. The spirit of an equal experience for all within possible and reasonable is still there. Both in system and the people themselves. It's a shame to throw out the whole bucket of apples just because there are 2 or 3 in there that are no good. Same goes with this.