Hi,
my friend actually recommend mi to open the wine only during dinner. This is because the guests at his wedding dinner actually finished up the wine so fast, cartons even before the wedding dinner. Of course that depends on ur relatives and your friends as to how capable they can drink. However, My uncle gave mi another opinion, saying that i should open beer and not wine at cocktail session, cos he said people who are pro alcoholic drinkers will drink beer first as starters then later wine during dinner. Personally, i think it really depends on your budget. If your budget allows for wine to be taken throughout the night, then i dun see any reason for having any reservations for that. Otherwise, it would be really wise to open wine for dinner only.