what kind of labels or information are you wanting to add to your images? it depends on what program you use, when adding images to create a gallery, some programs may not be able to add information that may exist in the images properties tab. different photo gallery programs are likely to also be incompatible with one another when opening saved files that were made in another program, unless it states that it can use them. different image gallery making tools have different ways of dealing with each image individually and the ability to add a description to it or not. I would assume most gallery tools would save your collection as its own gallery file in the location you have chosen, so that your original images would not be altered in any way.
as for the tools that do not do this, a minority may well be able add permanent details to each original image and its descriptions- its all depending on the gallery program you use and its options you can set. perhaps someone can recommend a few gallery creation programs for you-it also depends on what the easiest way for you will be to view an image and its description. do you simply wish to create a family tree with family history/a description next it, only being able to see it via a computer? If not, and you are only seeking for the ability to add many images with a description, clicking back and forth, then perhaps a gallery tool that can create a final "slideshow dvd" with your images would be just as good an option.