Which is more in keeping with the sunnah in marriage witnessing,getting a large group of people to witness the contract,or getting the basic 2 to witness and inviting as many as 1 one can afford for a walimah?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

One of the conditions for the validity of marriage is the presence of two witnesses as the Prophet said: "Marriage without the consent of the guardian and the presence of two witnesses is invalid." [At-Tabaraani and Daraqutni]  So, two witnesses are enough for the validity of marriage as stated in the Prophetic narration. However, if more than two witnesses are present then this is better as this is more confirmative in achieving the purpose of the presence of the witnesses, which is to confirm that the marriage has taken place.

Allaah Knows best.