There are lots of organizations doing short-term mission trips.
When you start looking at particular ones, just be sure you check them out thoroughly, and read up on them.
Go beyond their own website, and see if they have detractors, and then see WHAT those detractors say.
The detractors might point out genuinely horrible things (things which can be verified, or which are huge doctrinal issues for you) or the detractors might talk a lot and say nothing of real significance.
: )
Either way you'll feel better after you've checked them out for yourself.