Order a small, fancy cake for the cutting ceremony, then have the baker provide frosted sheet cakes of the same flavor and filling that you'll serve to the majority of guests, says Lisa Marie Kincaid, of Fleur de Lisa Cakes in Santa Rosa, CA. (All the cakes should be sliced and plated out of sight of guests.)
Keep it simple. Buttercream and fresh flowers are more affordable because they're less labor-intensive than a cake with fondant, handmade sugar flowers and appliquéd decorations.
If you want a multitiered cake but need cake for only 100 or so guests, ask your baker to create fake tiers using iced Styrofoam for the bottom or middle layers.
To avoid a delivery charge, assign someone to pick up the cake rather than having your baker do it. Ask which designs are easiest to transport and set up, and if she'll pack it up for you.