For those of us that do not have to go to claim our bags, it has taken an average of about 70 minutes to get from the plane to the resort. So, if you are picking up your own luggage your time frame could look like this...
4:30 flight arrives, about 10 minutes to get to baggage claim and 15 mins to get bags. Now, its about 5ish. Head to DME checkin desk, go to bus line...about 5:15/5:20 now. Bus to SSR is about 30 minutes, but you could be stop number 3 of 3 which would add about 10 mins or so to the time. So, it could be about 6:15ish. Checkin...another 20 mins...6:35ish. Freshen up....6:50ish. Bus to MK....possible wait of 20 mins, then 20 min ride, then boat or monorail to Polynesian, another 15 mins. It's now past 7:30.
Yes, you may make it in less time....I have given you the 'worst case' scenario...it could take only 2 hrs to get it all done. I never make an ADR for less than 3 hrs. after my MCO arrival. I hate having to worry.
If I were you, I would have DME handle my bags, deliver them to my room. This would cut off about 25 mins of time. Then, once I got checked in at SSR, I would take a cab directly to the Polynesian. This way you would need 70 mins to get to the resort and then only about 20 mins more to get to MK. So....arrive at 5:00, get to SSR by 6:15, then cab to Polynesian...arrive there at 6:35ish. But, you may want to freshen up at SSR, so add another 10 mins to that time. Waiting for luggage at the airport and then having to take WDW transportation to the Polynesian will add a ton of time.