You may think that mice cannot do anything until the shaman uses something to help the mice get to the cheese because of the way the map looks, but since this map was created with collision and low-gravity features, you can get to the cheese without the shaman.
The purpose of this map is to use the other mice as stairs. However, every other mice rushing for cheeses and firsts will be doing the same, so keep away from them if you're not looking for another stepping stool right away. When working together, the minimum of mice needed to complete this level without a shaman is three.
Most shamans will just build a trampoline or spirit the mice to the cheese, but ramps and so on are still a viable strategy here. It might be best to back out of the crowd and wait for many of them to return to the hole, and then assist the stragglers with your method of choice when you have enough space to work. You can also make a straight wall going up, to serve as a mouse-jumping method.