Hi. Is there a different way to cut 3" wedding cakes from 4" cakes? Will there also be less servings? Thanks in advance.

The best way to cut neat slices of tiered wedding cake (by indydebi):

http://cateritsimple.com/_wsn/page19.html

Whether your cake tiers are 3 or 4", the number of servings will be the same if you cut them all to be 1x2 (x either 3or4). (The height of the slices will be different, of course.)

Link to all four Wilton cake preparation and servings guides:

http://www.wilton.com/cake/cakeprep/baking/times/index.cfm

HTH