Print all 4 models. I think a layer height of 0.2 is ok with an infill of 20%. 

Tablet holder right and left are the same. When everything is printed, first put tablet down with the two right and left assemble and last then tablet holder up. If it is a bit too tight, you can help a little with a file. I just don't know if it works with an iPad. Since I don't have one, but maybe you can adjust it in the slicer accordingly. 

good print ....