A couple more thoughts: be prepared for a lot of standing around doing nothing to wait for something to happen very quickly. If you have visions of taking 10 people and getting a great viewing spot on the finish line, we should probably pop that right now. You'll either need to shell out for VIP passes or beat every other cycling fanatic in Europe to the line.
If I were you, I would fly solo that day. Take the train if you can as normal routes near the route could be blocked off. If you don't already have a hotel anywhere near the TdF route, book it now.