I have a fraternal twin brother with microdeletion 22q11.2 (velocardiofacial syndrome). what are the chances my children will have the same disorder?

Minimal: These odd micro-deletion syndromes are thought to arise as new defects which could be dominantly passed. Unless you carry it, you won't pass it to your kids and they would have the same risk as the general population to acquire it (new). You might benefit from discussing any and all genetic risk issues from both sides of the family with a geneticist.