You’ve got some awesome ideas going, @mary25- I especially love the Kitchen Magick ideas! 
Have you considered using edible flowers too? 
They make some gorgeous decorations on the cake and flowers carry magickal meanings of their own. Pansies, natursiums, and mint leaves are some of my personal favorite natural cake-toppers 
If you’re feeling particularly fiery, you can also dose the cake in a quick layer of alcohol and light it on fire- burning away the woes and worries of the past year and beginning the new year like a phoenix rising from the ashes 
. The witch’s cookery on YouTube has a video with a flaming cake (a Yule Log) that has video instructions on how to do so. This is probably where I should add that I’ve never been able to light a cake on fire successfully- haven’t quite mastered the trick myself 
You can also use a bit of Knot Magick while tying bows and wrapping presents 
Hope you can find some fun new ways to add a bit more magick to a b-day, Mary! Blessed be! 