What is the best way to get from Logan to the Omni Parker House at 8PM ??

Helicopter.

Quickest way is to take a cab. Omni is downtown Boston, not too far from the tunnels, so trip will be quick. If you're budget minded, take the airport shuttle to the MBTA airport station (blue line) and take the train to the old state house on that line, it should only take about 10 minutes. The omni is two blocks from the stop. Trains run through the night. Check out the mbta map on line , I think it's mbta.com

We missed trying the original Parker House Rolls here. Please report back if you try them! Thanks

At 8 p.m., traffic should be very light, and the trip fairly quick.

I don't think it's worth it to take the subway. You'll probably be tired if you've had a long flight, it will likely be dusk outside, and Boston streets are not the easiest to figure out.

Your trip should be no more than $10.

Brings to mind the old limerick..
"There was a young lady named Kroll,
With manners exceedingly droll.
At a masquerade ball, dressed in nothing at all,
She backed in as a Parker House roll."

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See website for the hotel, under 'hotel services' ...
http://www.omnihotels.com/hotels/default.asp?topic=services&h_id=20

"Boston is well-served by ground transportation companies that provide service throughout the city.
Hotel concierge can arrange car rental, limousine and town car service."