Activity ideas for assessment

[Cori21]

I am being assessed in placement soon with babies (under 12 months) and I have to plan an activity to do with cognitive. I know this involves anything but I am struggling for ideas due to the age of the children. There will only be 5 babies maximum between 8 months and 12 months. I was going to sing songs to them but the EYP said they won't sit and listen. I want to do something different though rather than just singing. I only need to plan one activity but the assessor stays for an hour so I will probably need to do a few things!
I decided against a messy activity eg. Cornflour gloop, because if they lost interest and went onto another activity, it would take time to clean them up when I am meant to be getting assessed.
I thought about a treasure basket, not necessarily with all natural items in, but with various small toys from the baby room and toddler room. But with treasure baskets aren't you supposed to sit back and let them explore? Apart from commenting on what they are doing it would look like I'm not doing much.
Any ideas on what I can do that will last an hour?