Have you considered changing them to Categories? Categories and Tags are essentially the same thing, just that Categories have a Hierarchy. Category selection is via a Checkbox so you will have more control over what is selected.
Update
If you have used the function ‘register_taxonomy’ to create your Tags then you only need to add or adjust one variable – ‘hierarchical’ – which needs to be set to true. See: Codex information on register_taxonomy
If you used a plugin to create the Taxonomies it should have a similar option. Remember to backup your website before you make any changes.