Weight - Mushrooms at a Concert/Weight Questions

[frenchywife]

SWIM and her husband have plans tonight to go to a concert and are staying at the hotel where the concert is being held. The amenities of the room include a spa. SWIM and her husband plan on enhancing the concert experience with some mushrooms of the Mexican variety. The actual plan is to consume barely enough for the concert (maybe 1 g each) just to have a slight buzz and then re-dose after the concert when SWIM and husband are in their room alone (1 - 2 grams). Is this a good plan? SWIM is not sure of the actual dosage recommended for such an experience. SWIM just knows that they do not want to be tripping really hard during the concert and that it would be best to do that when they are in their room relaxing in the spa ALONE.

Also, SWIM doesn't have a proper scale and wondering if the number of mushrooms is relative to weight. For example, if SWIM takes 3 whole mushrooms, is this equivalent to approximately 1 gram? Is there a way to tell without using a scale?