Capello's youngest son, 36-year-old Pierfilippo, is tying the knot with his partner, Tiziana, in Milan.
It was originally intended that England's friendly against world and European champions Spain would be played on Friday evening but the match was put back to Saturday as Barcelona - who provide eight of the Spanish squad - play on Wednesday night against L'Hospitalet in the Copa del Rey.
Capello's wife, Laura, will be attending the wedding ceremony. England host another international friendly against Sweden on Tuesday and Capello has no plans at present to return to Italy in between the two games.
England's players will be given time to relax on Sunday but will have to report back to the team hotel in Hertfordshire in the evening.
All 25 members of the squad are expected to meet up on Wednesday before training for the first time on Thursday.