The following day, November 1 is a holiday in Belgium. It is the day when one remembers ones ancestors, the freshly decorated cemeteries just have to be seen.
Halloween is a day/evening for the young, visitors shouldn't impinge on their activities, although if you happen to be staying in accommodation rather than a hotel, you should be prepared for the possibility of youngsters at the door seeking sweets.
Halloween is not really celebrated in Bruges, and children don’t go to ‘trick or treat’. The whole week is a school holiday and November 1 is a national holiday when everything is closed. (Shops, banks) Brugge is a tourist city so many restaurants and bars stay open.