To be fair the 'facts' are level 3 maths, so lower ability children in year 6 would only just be learning them. And the why part is in the year 5/6 QCA unit, so it is unlikely they would have met these before. Definitely not a KS1 activity really. BUT the how many days in a week, months in a year, aspects of seasons are all in level 2 maths and so perfectly suitable. As are learning the names of said days and months. You could have cut outs of the planets cut to scale and have children order them in size and so on. The song about little men in a flying saucer is also good for counting. Anything alien linked would work. A nice investigation with legs/eyes and so on for aliens linking to times tables would be easy to find on the web, such things are commonly used.