You're likely to find that WR is a really good idea if you haven't been in the tropics before. The humidity can be overpowering and not just to your equipment. If you'll be in mountainous areas, the temps may be more tolerable, but the humidity is generally powerful. This being the "dry" season, you're less likely to have sudden drenching downpours of the June-Oct "wet" season. But coming from the lovely dry mountain air of Colorado to the tropics will be a change.
Which is just to say, take your WR equipment and only take something else if you think you'll be indoors for lens changes. You'll likely want to use heavy-duty zip locks and silicon packets to absorb moisture for everything. Or a dry box if you have one, but I wouldn't buy it just for one trip.
The other thing, as you mention, is dust. Amazingly in humidity, there's often a fair amount of dust. Yucatan's limestone dust gets everywhere. It's fine and powdery. Honduras has a similar limestone geology. So, WR. Did I say it enough times?
Your KS-2 or K-3 and DA*16-50 / 18-135 / 60-250 will be good. The 18-135 would avoid lens changes on extended outdoor excursions. The two heavier lenses could be used when not traveling far. Maybe one low-light prime could be added to the list of what you have. I doubt if you really need a new lens for this particular work, but if you can swing it, go ahead.
Will there be a secure room or place where equipment can be locked away in your absence? Petty theft is a much bigger risk than violent personal crime.
Bring highly-rated insect repellent. Dengue, Chikungunya, Zika, West Nile, and Malaria risks demand repellent full time. Also, Hepatitis vaccines, tetanus up-to-date. Avoid stray dogs unless you've had a rabies vaccination. Review the CDC link. It is very realistic, especially the part about postexposure rabies prophylaxis possibly not being available in rural areas for animal bites.
Health Information for Travelers to Honduras - Clinician view | Travelers' Health | CDC You'll have a blast on this trip. Sorry if I'm depressing, not intentional. You've got to be prepared for things we don't frequently encounter in the USA.
I'm sure your friend will take good care of you.
Can't wait to see the photos!
Maybe I've said too much.
P.S. I echo what Woody said!