Limo Bus to Kawaguchiko during Golden Week?

We're staying at a hotel near Shinagawa station in Tokyo and booked a hotel in Kawaguchiko for one night on Sunday, May 6. We will be taking the limo bus back to Haneda airport to catch a flight to Osaka on Monday, May 7.

It seems like the limo bus is the easiest and cheapest way to get there and back, but I heard the highway congestion can get pretty bad. Does anyone have any experience taking the limo bus to that area around this time? We also have our luggage with us which is why we were hoping to take the limo bus rather than the train. I'm ok with a delay of maybe half an hour but if we're sitting in traffic for hours both ways we'll miss our check-in time in Kawaguchiko and our flight at Haneda.

Thanks in advance!!

6 May traffic jam is coming back to the city center of Tokyo, the bus leaving the city center is fine.
7 May is also hard to imagine that bus will be too late if not in btw morning or evening rush hours,
but if a big traffic accident happens it will not restart soon, train is pretty safer.

Also you may not have read Limo bus rules.
http://www.limousinebus.co.jp/en/information/useful/baggage.html