Yes! You just need to follow the terms of the GPL: provide a copy of the license text, and either a copy of the source code, or a written offer to provide the source code on request. If you're distributing an unmodified copy of the installer, you can probably get away with just a mention of its source (e.g. the license and a link to where you originally downloaded it), but you might want to contact the Linux Mint development team to double check. I'm sure they'll be happy to hear you're including Linux Mint.