I am making a cake for a friend's mother's 80th birthday and it needs to be round, two tier with a bow on top and serve 60. Would a 3 layer 6" look OK on a 3 layer 10"? Thanks ahead of time for any advise.

Unless you put the 3rd layer on it's own board, when cut you will just have an extra tall piece of cake and the servings will not increase. Using a cake board w/the 3rd layer will allow 1/2 the # of servings cut from the 2 layer cake so you should end up with about 50 servings from the 10" and about another 18 or so from the 6"er (12 from the 2 layer + 6 from the 3rd layer.)

Cutting and serving a 6" high cake is a pain regardless of what size it is. The pieces look very small on plates...

Two-layer cakes 12" and 8" round look nicely proportioned if they end up 3.5-4" high, and they will serve the required number of people. They do not look "large".