You are confusing me ... if you are filing a return and claiming the child you MUST file it attached to a W-7 to get an ITIN. If you are not filing a return then you have no reason to get the ITIN.
As to the FSA ... to use that program you must have a qualifying child that you claim on a return which again means you need the ITIN. If you put money in an FSA and then don't file a return OR file separately then the money you put into the FSA will simply be added back into your income on the tax return which negates the entire reason for the progam.
