It is traditional for the couple's parents to meet if they have not already done so once the announcement has been made.
The bride's mother traditionally writes to the groom's parents, expressing delight at the forthcoming marriage and suggesting that a date and venue be found for both sides to get together.
It is inappropriate to leave a first meeting until the engagement party, and highly inadvisable to leave it until the wedding day.
If the parents do not already know each other, meeting in a neutral environment such as a restaurant may be a good idea, so that no one carries the burden of playing host or hostess. The bride and groom should make every effort to put both sets of parents at ease.
Remember that first and foremost, this is a celebration. Any initial awkwardness is usually forgotten once the discussion of wedding plans is underway.