Not silyl at all, but you needn't worry.
It doesn't really matter which name you use, as a name isn't material to either application, as they clearly relate to the same person.
For your son's passport application, just use your married name. You will probably enclosing your marriage certificate in any case.
Same with your spouse visa. While your passport still carries your maiden name, there is an observation that it has been changed. Again UKBA will know they belong to the same person as your marriage certificate is attached. Also on the application you have to state any previous names(s) you have been known by.