as i have received so much help and assistance i thought i give you a short update.
(all images copyright lukas lang building technologies)

last week i was able to finish the viz renders for our kindergarten project.

for the grass i made a vue rendering with grass blades and used that pic to create a seamless pattern which i overlayed to the grass material in vue (in post). i just was not happy with any grass vue would show me :) maybe i have to play around more ... the people are aXYZ meshes, good for midground, probably not for closeups. the lower foreground grass hill was not liked to the image was cropped! easy and fast solution.

here i would have liked to have more time to work on the upper left corner. would want to create better road and neighbourhood ...

the two foreground babies, the grid on the roof and the background landscape was edited in as i did not have the time and ability to create that in vue in time. the rest is all vue GR rendering.

the first two images (all at 2400x1500 resolution) took about 10-15 hours with 3PC's and the last where i could use all 5PC's (all dual socket quad core xeon) over the weekend took almost 24 hours. all with final settings where i user defined sub rays to 10/10 and AA to systematic 5/10 100%

after my first "real" project with vue i am quite happy how well it works. esp comparing it to making trees and other natural stuff in maya or blender. the only thing i would like to be better is the AA of "technical" meshes (basically anything with straight lines) at lower resolutions. but i guess everything is optimized for natural chaotic stuff in vue and at higher resolutions required for prints the AA is ok.