Aoife,
I can see that as being a really nice maths activity, about order and distance and temperature.
I’d have a table up on the whiteboard with some basic planet facts — perhaps the language of near and far, hot and cold, big and small, with perhaps pictures of the colours of the planets. Just think of the sorting that could be done as well!
Can you put the planets into 2 groups — tell me what each group has in common. (could be 4 nearest the Sun vs 4 furthest from the Sun), (could be 4 smallest vs 4 biggest), could be the ones Earth temperature or warmer vs the Earth temperature or colder – this is a bit tricky, since temperature varies so much!