We usually rent a car instead of taking the Magical Express and that takes about 1 1/2 total to get our luggage & rental car, drive to WDW and check in. Magical express may be just as fast, but it does stop at multiple resorts so it might take a little bit longer. 3:30 to 5:00
Your best bet is to take the bus from ASMU to MK. Figure it's about a 25 minute ride and give yourself an extra safe buffer of 15 minutes to wait for the correct bus. Nothing like watching 8 Downtown Disney buses go by while you're waiting for you MK bus.

5:00 to 5:40
You can walk faster to the Contemporary for Chef Mickeys - 5:40 to 5:50 - so say 6:00 p.m. for Chef Mickey's.

There's a boat that if you time it right will take you to the Grand Floridian for 1900 PF. Or you can take the Monorail. That will take you about another 20 minutes for GF, plus possible wait time for the monorail or boat. 5:40 - 6:10 - so say about 6:20 p.m. for 1900 PF
You need to hop on the Monorail to either Ohana's, probably 15 for Poly and possible wait time for the monorail. 5:40 to 6:05 - so 6:10 or 6:15 for Ohana's.
