... then you can pick parts which use a somewhat smaller ensemble. Below are some suggestions on such parts.
Part 3
Soprano solo with woodwinds, marimba and strings
Part 6
Mixed choir with cor anglais, tuba, percussion and strings
Part 8
Double choir solo a cappella (alternatively double quartet)
Part 9
Four soloists (Soprano, Mezzo soprano, Tenor, Bass) with woodwinds, trumpet, percussion and strings. Solo role for the viola.
Part 16
Tenor solo along with horn solo, plus woodwinds and strings
Part 17
Three soloists (Soprano, Tenor, Bass), mixed choir and chamber orchestra
Part 18
Four soloists (Soprano, Mezzo soprano, Tenor, Bass) assisted by ladies choir, along with woodwinds, percussion and strings
It is also possible to consider other alternatives if it helps you create a performance. There are piano reductions available for some parts and more can be made (or perhaps versions for organ).
Another suggestion is to pick the parts which concern those Human Rights which have your particular interest. Just check the text out, simple as that.
At any rate make contact and let us know if you have ideas.