if you use Linux (I think you are) you can use jhead to copy EXIF information from one JPEG to another so you do it like this:

convert IMG_0111.jpg -size 1024x768 scaled/IMG_0111.jpg 
jhead -te IMG_0111.jpg scaled/IMG_0111.jpg

Or as a script

mkdir scaled
ls | xargs -iASD echo 'convert ASD -size 1024x768 scaled/IMG_0111.jpg;jhead -te IMG_0111.jpg scaled/IMG_0111.jpg '|sh

PS. Did you get GPS logs from your Garmin?