Getting to the reception from the ceremony- thoughts? (nyc)

I want to have my ceramony and cocktail hour at one location (the James Burden Mansion in NYC) and then reception at another place, that's anywhere between 20-40 mins away depending on traffic. I'm thinking of providing a party bus and highlighting cool NYC sights along the way for out of town guests. A bit of a city tour. There'll be light drinks and music, but I'm still worrried people will be bored. Do you guys think this is too long? I used to be dead set against two venues in NYC because I hated the idea of dealing with the traffic- or subway! But I've fallen in love with two different venues and really want to have both.