Honestly, if it were me, unless you are really close to your step-day or an uncle, I would just walk down the aisle by myself.
Your close friend will make your DH uncomfortable, and just thinking of my ex walking me down the aisle would be kind of like sanding a piece of wood accross the grain. To some people, me included I would be thinking "wow he gave her permission to marry again"...Not An Option! Not trying to offend here, its just my opinion.