OK, not my first choice, but he's fine. Heard a lot of good things about his live shows, plays big venues in the UK and should be a good sing-a-long. Standard and appeal of headline acts this year is pretty poor though. He's massive in Newcastle!
There's no downside to them pushing it back a week or so, they'll still sell it out. However there is a downside to pushing it on a week where socials are flooded with posts about charities and support for people still affected. Also loads of artists are based in LA (such as Trent from NIN).