I've had it take as long as two hours, without getting my own luggage, from arriving at DME in the airport to arriving at the resort. It's happened to me twice. So while 90 minutes may be the average, it can easily take longer than that. And of the few times I've had to get my own bags, it took at least 30 minutes more. We've found baggage claim at MCO to be a bit slow and crowded too.
If your plane lands at 5:30, the earliest I would make an ADR would be 9pm. If you let DME collect your bags and all goes well, you'd get to the resort by 7-7:30, check-in, drop your stuff off, and then hop on the bus (presumably) to your ADR. Personally, that would be too late for me after traveling and I'd probably opt for QS at my resort or even visiting DTD and grabbing QS there.