Madonna has tapped Sir Elton John to perform his instrumental tune, Song for Guy, at the reception following her Scottish wedding to filmmaker-beau Guy Ritchie. The nuptials are scheduled to take place Friday at Scotland's Skibo Castle. According to the Daily Star, security will be so tight that guards will use mirrors to look up guests' kilts in search of hidden cameras. In addition to John, pop star Sting also reportedly will belt out a tune at the reception. Meanwhile, US Weekly reports that the festivities will set the Material mom back about $3 million.