We loved commonwealth as well, especially because their staff is the most responsive out of all the schools we considered. They have a ton of extracurriculars (music, dancing, sports, etc) but are mostly offered for the older children. We eliminated them because of their location and the fact that we have pre-k and a kindergartner. Our school rankings were:
TASIS
Commonwealth
St.Johns
and so the decision was between gated communities/suburbia or city life and what schools were best for our kids age. So we decided if we were going the suburbia route we'd do Dorado + TASIS since it was our favorite, especially at around 4th grade because of the robotics and programming classes.
But since neither school had great offerings for extra curricular until 4th grade we decided that St.John's was best for ppk-4th. St.John's has PE more often and they do less transitions which is good for younger children. They are also the only school with a full time psychologist on staff.
So we are going to do St.John's until 4th grade and keep an eye on Commonwealth. If it gets more programming classes by then we might consider it over TASIS. It is in a much more affordable area than TASIS, so if you want a good school in a gated community that is more affordable than Dorado I would highly recommend commonwealth. Especially since you have a 5th grader who could take advantage of the programming classes.
If you do take advantage of Gersh for your younger, I would say go with St.Johns. They are in the same area so it'll be easier on you.