Awesome!
A big part of performing a demonstration of skill like this is keeping it interesting for the average layman, and that means speaking while you do it. Nobody just wants to watch somebody quietly deal cards. A good story or patter line also gives you natural cover that can disguise any minor pauses or inconsistencies. The fact that you're this smooth at it while silent is a very good thing! I would if delivering patter while doing the sleights would affect your performance positively or negatively?
Scott.