No doubt this is going to be a fun and exciting event. There are several ways to get here. You can reserve a campsite and get here early Monday. You can ride your bike up which would be especially nice after the road closes to general traffic at 1:30 Tuesday.
Another great way to get here is to ride the Summit Stage. There will be buses running between A-Basin and River Run at Keystone at the following times.
Monday 4-10 PM
Tuesday 9 AM - 2:30 PM amd 6 PM to 10 PM
I would try and get here a little early. Do not wait to catch the very last bus.