Oh are they supposed to be aliens? I thought it was some weird "mustn't give offence" marketing policy to use an everyman family that wasn't black, white or any shade in between.
Yeah, that's probably about right. Certainly you're not going to find December 25th 1914 listed as a date of an official England v Germany organised international football match. (And I can't believe No Man's Land was as undamaged as it appears in that advert).
There were several football matches, although 'matches' is probably too formal a word and they were probably little more than kickabouts - and not necessarily using proper footballs either. It depends what you mean by 'firm evidence' though, there's obviously no YouTube videos, and official...