I would definitely book the later flight. When one needs assistance, one has to plan on everything taking extra time. If by some chance, their inbound is early or things are looking good, AA may very well rebook them onto the earlier service depending on the flexibility of their fare and an agent willing to do so (not qualified for SDC).

I can fully appreciate the decision not to overnight as it involves multiple additional movements, none of them pleasant. I would nonetheless have done the research on DTW hotels which might suit in case of IRROPS and not rely on IRROPS handling by AA.