I think that ImageMagick could be a great choice. It shouldn't be too difficult, for example you can try this command:
montage $Child_HF2_5*.png -tile 1x3 -geometry +0+0 $Child_HF2_5_FULL.png
In this sample command I had 3 images, so I used -tile 1x3
; if you have n images you'll have to use -tile 1xn
input:
output: