This is a great investigation which the children absolutely loved doing. I adapted an idea from the Young Archaeologists activity ideas and developed further for an enquiry based lesson. It was judged outstanding however you could do a quiz at the beginning instead of a guided session to engage the children further.
You will need to make the 'poo' the night before before it's great fun and don't reveal it to the kids until they get back to their tables. I used pieces of jute I had lying around to cover them up. Provide tools for 'dissection', number each poo (you will need the three different types of poo per table) and pin up the ingredients cards at the start. The investigation gets interesting when you reveal the Egyptain character stories at the end and they have to work out 'Who's Poo is Who?
I did follow this up with a piece of extended writing to demonstrate what they had learnt.