Yeah, I was thinking that after I wrote it. If there are two adults, could one run ahead to get the DAS reservation so the he doesn't have to go to the ride himself?
Also, I thought I read somewhere that there will be some DAS kiosks so that you can go there rather than the ride itself, although I am not 100% on this.
I think that FP+ may actually be better for you than old FP as you can plan ahead more. I also recommend a nice sit down meal during the day, even better if it is a character meal so you can avoid having to queue for those as well! But I am probably telling you what you already know!
It's a tricky one but it seems a shame for you to have to stop going. I assume your son likes going? I know our daughter loves it, I think she likes the sensory stimulation although I know some are the other way. Good luck whatever you decide.