Yes, Cliff and Ann can get married whether or not you see all the heart events. Getting Cliff to work at the vineyard just guarantees he'll be around to get married.
The girls get married off around year four so it doesn't matter what heart level they have for you by then, 'cause they will marry off on their own to their rivals. Just be sure to marry the girl you like before then, and with Cliff and Ann, there are two more rival events that happen after the blue heart one at the Church, so you still have a chance. Good luck
