When dd was about 4 I think, she attended a brilliant drama workshop at a museum in Berlin. The theme was the tower of Babel (might be too religious for you but to give you an idea). Dd absolutely loved it, they were there for 2 hours IIRC, had a break in the middle (they all had brought a drink and lunchbox with them) and then put on a little performance for the dp. They just loved doing that bit.
I wasn't there for the workshop but as I understood it , they worked in pairs with big cardboard boxes which became planes, cars, buildings etc. It was really quite clever and very good for dc their age.
This is 5 years ago now so I can't remember the cost but since it was a museum activity, it would have been subsidised anyway. Wasn't much. My dd was still raving about it 4 years later.
Definietly a theme they can be totally imersed in.
In my opinion - not particularly ecperienced but lead workshops and have a toddler
Time - morning, from 9 - 10 [break] then 10.20 - 11.30 perhaps... ALso any wet craft suff can dry over break
Activities - dance, making a mask for dance, some basic role play [based on animals/nature perhaps], not too complicated more immersed in theme and lots of enthusiasm. Drama - can the family make a washing machine/tree/bridge etc with all their bodies.
Age range - from 3-5. My 2 year old can;t talk enough to cope with it I don;t think...