Better late than never, the Knicks have finalized plans to hold a special 50th anniversary celebration night March 21 to honor their first championship team of 1969-70, The Post has learned. All the players from the Knicks’ first title team have been invited for a Saturday fete as the Knicks play host to the Warriors. The wrangling was finding a proper date to ensure the most players could attend. Last month, at least two of the former 1969-70 players were privately surprised they had heard nothing from the organization about a golden anniversary night.