Courtyard access, access paths paving or concreting

I'll join in....

Is there any reason not to use the classic grass pavers as a paved surface?

I'll join in....

Is there any objection to using the classic grass grid stones as a paved surface?

The regular grass grid stones, including the grass in the gaps, are very maintenance-intensive. The grass needs light, water, fertilizer, and must be mowed regularly (at least once a week). That actually means you shouldn't park a car there for an extended period. You also can't walk on it with heels. If you don't do all that, weeds grow everywhere, the grass turns yellow, and it looks very unkempt. Regular eco-paving requires much less work.

Best regards Sabine

I don’t have a specific manufacturer in mind yet. Let's see what the contacts from the architect come up with. Otherwise, I have only found a few manufacturers online so far. I would prefer green ground grids....

I have already seen them nicely done. Often you don’t even realize there are ground grids underneath. They are sometimes also used on golf courses. The same applies as with the lawn: water, fertilize, mow regularly...

are not that slippery, especially since we are planning a footpath. But only conditionally suitable for high heels.

Many things! Grass pavers are ugly. Lots of gray, little green... Better to do everything with drain asphalt, eco-paving... Especially since the lawn usually grows poorly. Due to the unfavorable ratio of "stone" to soil, the lawn quickly burns out. Lots of water is necessary.
With ground grids, I would have continuous grass and green. The ground grid takes the load off the roots and stabilizes the whole thing.

Mh my children quite like to ride their bikes, balance bikes, pedal cars, sliding cars during the day in the yard...

The lawn with ground grids is more durable than "normal" lawn. Given the load you mentioned, I would rather not consider it. Two cars drive in and out here daily. Except when we have visitors. So, it's not a real strain. I would like to have even more green as a contrast to the concrete walls.

It's not about the burden, but about the possibility for the children (if available) to also move the mentioned vehicles around the yard sometimes. And not always having to start from scratch. Likewise when friends are there. Lawn, lawn grids, gravel, etc. are rather hindrances. Maybe not the main aspect, but at least worth thinking about.