I would be as worried about flight delays as I would about DME.
The average DME time reported is 70 minutes when using the luggage delivery, it can be as quick as 60 or as long as 90. Add to this time if you have to stop for the potty, water etc and if the lines are long at DME or if your the last of the 3 stops.
I think your cutting it very close even a long check in line could make you late! IMHO if your doing any ADR's I would do dinner and only those that don't require a non-refundable deposit.
I travel alot and even the best plans sometimes go bad! I rarely make firm plans for arrival day, just to much can go wrong and I don't like to add the stress of making plans. We usually play it by ear, a pool swim and quick service meals on day one just in case.