Hi Ciara, this sounds like a really lovely lesson. The children would have such a fun time making the different planets using balloons. A few years ago, I did a similar lesson with 1st class about planets. We, as first class teachers, decided to link a lot of our literacy and art activities with our science lessons that month and as part of this the children designed their own planet, its composition, its inhabitants or lack there of and its orbit. I was amazed at how much they had picked up from the lessons and included in their designs and their writing. They had planets lying on their side like Uranus and planets spinning the opposite way like Venus. Space really is such a great way to inspire their love of science.