RCD – there are lots of threads have a search.
Just have one of you buy all the tickets, you’ll need names and dates of birth for all the riders.
There are the same number of tickets for sale at each start point. The bigger resorts are potentially busier as there will be non PPdS riders queuing, however in practice you’ll be starting earlier than riders not doing the event. We stayed in Les Gets last year and officially that was out start but we rolled down the road to Morzine and only had a short wait.
Plenty of trails of all types from XC to full on downhill. We had a wonderful lunch at a great place with stunning views, above Les Gets, Mont Caly, accessed via a simple ride from Les Gets lifts with various options down (Dans le Gaz black one of the easier ones locally). Lift passes are cheaper than for skiing and highly recommended, easy to buy by the day.