This would be my best offer (if another team offers more, they can have him):
Tatum, MLE Player, Baynes or Williams, Yabusele, Kings pick, Grizzlies pick, Clippers pick, Celtics pick.
If the Pelicans want Tatum, then it means that Irving, Smart and Brown are off-limits. Rozier and Morris are also available for sign-and-trade scenarios, but that seems hard to pull off. Would it be necessary to expand the trade for salary matching purposes, then I'm willing to put either Hayward or Horford in the deal in exchange for Holiday.
By the way, I'm totally convinced that Ainge will trade for Davis and that Irving will re-sign, the only thing I'm worried about is the price that we're going to pay. I believe that Irving, Hayward and Horford are safe anyway, because they have more value to the Celtics than to the Pelicans.
But I hope we don't trade away our longterm future for a 4-year window based on the duo Irving/Davis with help from Rozier/Hayward/Morris/Horford/Baynes and ring chasers.