I propose that you become another toilet the area of the closets that is adjacent to the existing one. In this way, you will solve the problem by renouncing only part of the entrance surface and the affected children's bedroom will continue to have a storage area, although somewhat smaller.
We have divided the space into three parts. On the right, the shower, with the recessed plate so that it is at the same level as the floor and isolated by a transparent folding door. On the left, and in a hole of the same dimensions -80 x 80 cm-, the toilet is located, which takes advantage of the downspout of the neighboring bathroom. Finally, in the center we place the washbasin area, 1 m wide and 0.50 m deep. Its sides host two closets on the other side. In all three areas the ceiling has been lowered to add one more element that harmonizes the environment.