Hi Susan! Many thanks for your reply and suggestions. I would have to say that the prospect of doing this starting in just over 36 is hours is moderately terrifying!
You've hit upon my primary concerns there: the children's development at different ages.
Here in Bavaria children start school at seven (some sooner) and many go to kindergarten.
One who is defintely coming is a hyperactive 6-y-o boy of elementary level. Of the others, there are two girls - sisters - aged five and seven who know a handful of words each. There is another boy aged seven or eight who is a low elementary. Any others that may turn up on the day are as yet unknown.
The children here learn no English in school, and have widely varied L1 reading/writing abilities.
I may have enough ideas to do at least the first two sessions, after which I'll have a much clearer idea of the nature of the group. My plan is quite loose in that I have a number of activities and will choose which ones to use as the first session develops.
However, it's still the biggest challenge I've faced as a teacher for over 20 years with so many variables and uncertainties to contend with.