I am helping friends on their wedding day that they are hosting at home. They have a restaurant (located 45 minutes away) that will be delivering pasta dishes (chicken alfredo, spaghetti and meatballs, and a vegetarian pasta) and garlic knots for the backyard reception. They have rented chafing dishes for the food to stay warm and when they have dinner, around 6:30 pm, they'd like us to take the food from the chafing dishes, place on family platter plates to be placed on the tables for it to be shared.

What time should I have the food arrive if dinner is to be served by 6:30 pm?

Shall I already have the chafing dishes hot and ready for the food arrival beforehand for the transfer?

Where should I keep the garlic knots to hold their heat?

Any other tips or suggestions?

Shall I already have the chafing dishes hot and ready for the food arrival beforehand for the transfer?
Absolutely, and the Sternos only last 2 hours, so you need 2 sets for each pan, and tongs to get the hot empty ones out.

Where should I keep the garlic knots to hold their heat? Tricky. Put in large paper bags and keep in the regular oven on low heat- bring out to serve.

You desperately need appetizer areas and here is an excerpt that explains why:

Before the Buffet; Why You May Need an Appetizer Table
A self-catered buffet is a real challenge to the organizers, and things don't always come together as smoothly as hoped. By planning and setting up an appetizer area or "nibble table" which is ready when the guests begin to arrive, the cooks and servers have time to complete the arrangement of the dinner buffet. This is especially critical if there are children among the guests, or there is a wait before dinner, as at a wedding reception.

This does not have to be complicated. Three items, plus a punch, or two if one is alcoholic, are sufficient. Typically, include a fruit tray, a cheese tray and an attractive dip or spread; or you can go with a dinner theme such as TexMex with chips, salsas, Texas caviar and guacamole; Italian with bruschetta or antipasto; maybe shrimps or other cold seafood, if budget permits.