Pumping in the car really isn't a big deal. I've done it too many times to count. Rather than use valuable opening park time going to the baby centre, taking care of business in the car before hand is probably the best option. This also gives you the option to leave things in the car afterwards if your wife wishes to/can. A nice large cover helps when pumping in the car. Also, when pumping on the go like that the Medela wipes help. There's a great thread about this type of stuff on the Family board.