In our countries, we customarily make Kiddush in shul on Shabbos and Yom Tov except for the first night of Peach. (MB5)
It is a mitzva to buy the wine for the Shul’s Kiddush. (MB5)
The minhag is to stand for this Kiddush. (Rama)
The chazzan should not drink, only he should give a child of chinuch age (about 6 or 7 years old depending upon his cleverness) to drink the wine. If not, the chazzan should have in mind to be yotzay Kiddush and then drink a r’viis in order to count as Kiddush bimkom seuda. Don’t forget to say a beracha achrona. (ShA-MB1)
If you aren’t yotzay with Kiddush bimkom seuda, you aren’t allowed to taste a thing. Children below bar mitzva are the exception, the halacha does not afflict them by making them wait to eat. (MB1, 2)