as an ex support member I can state it's up to the giveaway creator. If you're happy with people entering for DLC, support will be too!

Yes, the choice is yours. When it comes to giveaways with DLC anyone can enter for them, even if they own everything since SG doesn't recognize the DLC due to the Steam API. The giveaway creator can submit a ticket if the winner has the base game or the majority of the bundle for a reroll. This is the reason you'll see people asking sometimes like RSDA if it's okay to enter for the DLC. You've mention entering for the DLC is fine so there's no issue. You will want to check the winners library though as they could own everything in the package because of what I've mentioned about the Steam API.

If you need assistance when this ends please reach out to me or submit a ticket and we'll do our best to help. :)

I'm interested in the DLC, so I'll be entering for this, ty.

it's your call, not their's. per the faq:

What are the rules for entering to win Steam packs if I currently own a number of the games contained within?
We ask users not to enter giveaways for packages if they already own the majority of the games. This allows for winners that will receive the most value out of their gift. In the end, the giveaway creator has the final say, and if they believe the winner owns too many of the packaged games, we'll allow them to request a new winner.

so basically that's why people generally just ask. if they win a package giveaway where they own any or all of the prize, the giveaway creator is within their right to request a reroll. it's easiest to just ask in the comments, or sometimes the creator will preemptively put it in the giveaway description.