I agree with Sco.
You really can't safely 'assume'. Between flight delays and variability on ME, it is hard to predict. (thunderstorms?)
ME buses often don't leave until they are relatively full. If you are last to board, the bus will leave right away, but the time between bus departures can be substantial. The last time I used ME, I spent well over 45minutes waiting to depart. Also, each bus makes multiple stops. Your resort could be the third stop, which adds quite a bit of time.
Also, if you are not familiar with MCO, the distance between your gate and the ME terminal can be quite far.
Odds are good it will be about 100 - 120minutes from the time you land to the time you are at your resort, but it could also be quite a bit longer. The last time I took ME, I was supposed to land about 4pm. The flight was delayed about 20minutes, I waited some time for a bus to arrive, then for the bus to fill. The drive was 30minutes, and my hotel was the third stop. I did not get to my hotel until after 7pm! (7:20pm, I think)
So odds are pretty good you will be at your resort by 4:30pm, and likely you will be there by 4pm. The shortest I've ever seen was about 45mintes from gate to a park. So you might also get very lucky.