Problem they are going to have with the new stadium - they need to inform, with 100% certainty, UEFA before February where their stadium is going to be for the knock out part of the CL - if Levy's "7th Jan with next update" means, effectively, they will be able to make a decision as to when to schedule the 2 test events, which will have to happen a week apart and probably 1-2 weeks after their announcement, they are leaving it very fine to hit the January deadline to tell UEFA yay or nay. Their next home fixtures after Utd are Watford on the 30th Jan, Newcastle on the 2nd Feb, and Leicester City on the 9th, followed by then the CL. I would imagine it would be difficult to persuade UEFA to allow the CL to be the first match just in case of issues. which leaves one of three decidedly unimpressive looking matches to potentially be the first.
And because of the FA's bending over backwards for them, they only have one more big game really left other than Utd - 2nd March vs Arsenal, which would be a fun match to open the stadium, but would cause riots with the fans, not least because it would mean they would miss the CL match and therefore would have to play at Wembley if they fluke drawing Porto and qualify for further matches.