I saw there are two options of day to trips to Paris directly through DLP. It just says on their website "see the concierge at your hotel for more information" does this mean there is no advance booking required at all??? just ask when we arrive?
Yes you can book in advance, i booked our day trip in December, and i booked the one the year before about 3 weeks before we went. I booked with a travel agent. They say if there is a specific day you want to do the tour, then book :)