You shouldn't change your plans. Although the murder was an absolutely awful event it is not the norm for Caye Caulker.

In regards to malaria and dengue - it is a true and credible concern and you should take the relevant precautions. If you choose not to take the pills (talk to your doctor) at minimum you should wear repellent and suitable attire to avoid being bitten.

Caye Caulker isn't for everybody, and if you decide it isn't for you then you can try the next island over, Ambergris Caye or move to another mainland location.

I am sure your family is going to have a memorable and enjoyable vacation if you come here with an open mind ready for some adventure and new experiences.