Great idea and generous of you.
Friends have done so in Mexico and Guatemala. They were usually nurses, PAs, and Drs who brought real expertise as well as supplies and they were going to an area in need (mudslides wiping out villages) and were welcomed with open arms and much appreciation.
Coming in cold, I would suggest immediate contact with the local health personnel and take your cue from them. Villages might not have any (or periodic visits), but regional health authorities might be found. Or village elders/mayors. If you know where you are going and speak Spanish, calling ahead might pave the way.
Eyeglasses, especially for reading, are always appreciated.
This, by the way, is a great way to get incorporated into a village and welcomed. I have been jealous of those friends who were “adopted” into a community.
It might be wise to decide ahead of time whether you wish to practice yourself or just deliver supplies.
Covid, of course, makes all of the above far more complicated.
Good luck, my best, Dick Stevenson, s/v Alchemy