Unfortunately even if people own everything they will still be able to enter. It's like that for all DLC, including games that have DLC with it, so you'll need to check the winner. Some DLC you can see without adding the winner as a friend, but the majority of DLC you'll need to add them.

Do you mind if people enter this giveaway for just the DLC or would you rather them not?

Yup, I have everything contained within this bundle. As FateOfOne said, DLCs and bundles are not registered with the library Steamgifts uses to see whether someone owns a game does not contain the information about these bundles or any DLC.

I will do my very best ;)