Can I See Colosseum Attic/Underground Together?

I am not sure what you mean by “Underground tickets (the individual ticket option, not the guided tour)”.
Access to the Colosseum’s underground area (the Hypogeum) is restricted and must be done as part of an official guided visit. Visitors cannot enter the underground independently, even if they have a “Full Experience” ticket.

Once the underground tour ends, you can usually continue exploring the regular Colosseum areas that are included with your ticket on your own. However, you cannot remain in or return to the underground section without the guide.

I do not know the answer to your timing question, but it might be a rush to get from the Attic to the start of the Underground tour in 25 minutes.

I have visited both the Attic and the Underground and I enjoyed the Attic so much more…the views from the 5th level are amazing
You can see the majority of the Underground from the first level on a regular Coloseum entrance ticket.

I can't answer the question about timing but I do believe they sell a ticket for the underground that isn't a tour with a guide per se, more of an escorted walk-through. It sounds like that's what you purchased. As mentioned, you won't be walking about down there on your own, and likely will be moved right along.

While I've not done the underground, I agree that you can see down into a fair amount of it from points above, and other posters who've done the attic have had very positive things to say about that piece so if I had to choose, I'd skip the underground.

Kate…you are correct. There are 2 different ways to buy tickets that allow access to the Underground.

1. The official “Guided tour of the Underground” which includes access to the Arena floor, Colosseum interior, licensed guide for the Underground, and usually Roman Forum and Palatine Hill access as well, and…
2. The “Full Experience–Underground Levels & Arena ticket” which includes Underground (hypogeum) access, Arena floor access, Colosseum levels 1 and 2, Roman Forum, Palatine Hill, Imperial Forum, and is for 2 consecutive days for the archaeological areas.

The Underground portion is always visited with an authorized guide or educational guide service. Even when you purchase the official “Full Experience–Underground Levels & Arena” ticket, the Underground access is tied to a guided component.

At least this is the way I currently understand what is offered…I am happy to be corrected if this is not correct.

I also scored both the Attic and Underground tickets for the same day (October 13, 2024). When I checked in for my attic time, I also mentioned that I had an underground tour ticket as well. I was told when I was finished with the attic to find one of the staff members and they would lead me to where I needed to be without exiting and reentering, and that they did.
My attic ticket entry was at 850am and I was escorted up by one of the staff about 10 minutes early, having the entire area all to myself for a good while before other visitors appeared. I headed back down around 930am and was escorted to the line for the underground tour.
I was concerned that maybe I would not have enough time to enjoy the attic experience, but I did and it was grand. However, IMO your ticket times do not allow a proper visit to the attic at all. I see 25 minutes between entry times, and this is not factoring in the time it will take you to get from the attic area to the underground tour meetup location. You have to be on time, they will begin without you.
Regardless of whether you do both or one, it's a cool experience. I enjoyed the attic experience far more, but with kids in tow, I feel the underground would be more interesting.
Have fun!

@NoNegativeVibes - Thank you so much for the response! Maybe there is hope we can do both. I also hate to rush the attic but a rushed trip may be better than no trip?