Roller shutters in the guest bathroom, yes or no?

On the page there is also a kitchen and on the 1st floor the children's room with electric shutters

In the east, it is guaranteed not to be sunny in the evening.

Touché ... Also true for the morning ...

on the side there is still the kitchen and on the 1st floor the children's room with electric shutters

Then also install the shutters in the bathroom. Otherwise, you will regret it forever. As already said, you can't add them later.
Of course, you have to wait for the extra charge, and if your general contractor(?) already omits them as standard, I fear the worst.

Ok, I will ask about that when we get to that point.

All other windows are equipped with electric blinds as standard, except for the bathroom and guest WC.

I also think it looks totally lame when individual windows have no roller shutters. IMHO, saving money in the wrong place. But that's just my opinion.

We refrained from installing them in the guest WC and bathroom and regretted it thoroughly afterwards. It faces east, and especially in the bathroom on the upper floor it becomes uncomfortably warm in the summer; the sun also hits the mirror exactly in the morning. The missing shutters annoy me massively! In the guest WC on the ground floor, I don't find it quite as bad.