Eddie Howe's side had initially been set to welcome Roberto De Zerbi's men in February, but that game was postponed due to United's involvement in the Carabao Cup final at Wembley.
United will now face the Seagulls at St. James' Park on Thursday, 18th May, with kick-off set for 7:30pm BST.
And the clash with the Foxes on Tyneside will now take place on Monday, 22nd May, with kick-off in that contest confirmed for 8pm BST. That game had previously been set to be played at 3pm BST on Saturday, 20th May.
Both matches will be broadcast live on Sky Sports.
Any further changes to the Magpies' fixture schedule will be communicated in due course.