See-throughs - long question

I have often considered setting up a blind taste test at the occasional
family get together, not only for vodka in this case, but also for
other products with "status" brands. For each group of products, I'd
figure on covering the cost spectrum as well as the reputation
spectrum. My in-laws are not heavy drinkers; but there are enough
social drinkers among them to come up with a sample size with possibly
meaningful results.

Serving size would be an issue if too many choices are offered. One
ounce x 6 is still 3 shots of straight vodka. Not so much for me; but
most of 'em don't have my blood volume or stomach lining. I don't want
a house full of puking inlaws at midnight. g

How much would be an adequate taste sample? And what would be a good
"neutralizer" to serve between tastes? Saltines? White bread?

Joe F.