For your second question about converting cakes from small to large. I have all of the basic wedding cake recipes already converted for you. I have not had an issue with multiplying any of these recipes. They are generally for a wedding cake to feed 150 guests. Here are the top three...
Your cake recipes if they are similar to mine should produce a fine cake when multiplied.
For your third question about the lace patterns. This is most likely done using sugar veil flexible icing. If you follow this link you can see and read more about Sugar Veil and order the icing mix, the mats and instructional's from Candyland Crafts, the company I refer my cake decorators to.
I hope that answers all of your cake decorating questions. If you have more as you get your business going feel free to ask. Good luck. Can you please let me know who to credit for these photographs and please send a picture of your finished cake and how you managed with your wedding cake.
Thank you very much for visiting! Happy Baking and Cake Decorating.