No brides parents, aunt and uncle "fill ins". Boutonniere, attire, corsage question...

So, my parents and I do not have a relationship and will not be at my wedding. My aunt and favorite uncle will be there. Were very close to them, and even though they are only 11 & 14 years older than us, they are more like parents to me.
My uncle will be walking me down the aisle.

My questions are:
1. What should my uncle wear? Or what does father of the bride normally wear?
2. Should he have a boutonniere that matches the groomsmen?
3. Should my aunt wear a corsage? My FMIL will be wearing one.