Make sure to reserve your spot and preferred time by booking online ASAP! We preferred the day tour for bright, natural lighting for photos; although it was VERY hot that day vs. the rest of the days we were in the city (mid April). There is free, yet limited parking across the museum, but it shouldn't be a problem if they only take in reservations and people didn't tend to hang around after the tour.
There were about 10-12 people in our group and we spaced ourselves around our guide (Carla) who was very enthusiastic, passionate and knowledgable about Vegas history and the signs. They don't allow you to stray away from the group or backtrack, but give you enough time to appreciate the signs and take in some photos.
Their museum will be expanding this year, so I look forward to coming back!