The Queen was the FAs patron and Prince William is the President of the FA, so it's quite a bit different to school or anything else. It is a show of respect from the whole umbrella of the FA, professional and grass roots isn't it for years of service from her, and from their Presidents grandmother nevermind the reigning monarch of the commonwealth.
All the kids who have done pre season, friendlies etc they won't hang up their boots or whatever over missing one weekend. I've spoken to my 2 who are 13 and 11 and they understand why the football has been postponed, so it baffles me adults have trouble getting their head around it.