Colosseum tour??? Help!

What day is your trip to Rome?

Aforementioned guide just relayed the information that at no time
during our stay are there any tickets left to see inside the
Colosseum.

This simply isn't true. Tickets for TOURS of the colosseum offered by the official website - specifically the underground - may be gone but general-entry tickets are always available and are not locked into any specific time or day. You can pre-order them here:

http://www.coopculture.it/en/the-colosseum.cfm

http://www.coopculture.it/en/colosseo-e-shop.cfm

Purchase adult tickets (€ 12.00 + € 2.00 reservation fee) and the € 2.00 reservation fee-only tickets for your children under 18. Choose the option to pick up all of your tickets onsite (at the ticket office reservation desk) as that's where you'll need to collect free tickets for your kids; you can't print those out online. Bring proof of age for your kids if any of yours are teenagers.

And do scroll down further on the page to "Individual guided tours"? Those are for the main part of the arena only and are only bookable by phone. If any of the days/times work for you and you want one of these tours, it wouldn't hurt to call and see what still may be open. Audioguides are available for rent as well (scroll down the page for reserving those). As you teach history, you might be able to get by with just prior research and a good guidebook; we purchased one at the bookshop there.

As previously stated, general-entry tickets are good until the end of December for any day, any time it's open, although if it's very busy the security check line may involve a bit of a wait, and also include entry to the Forum/Palatine.

http://www.coopculture.it/en/the-colosseum.cfm

Tours of the underground (mandatory: can't access on your own) offered by private companies are also available but usually cost quite a bit more. I think you and your children will be just fine with exploring the areas open under general-entry tickets, though.

Does this help?

Editing to add: your guide may be able to get in free as well or he/she can choose to stay outside while your family takes their look around.

List under "Free conditions":
...tour guides from the european union practising their professional activity;

Frankly, I'd question how good your guide is if they told you there's no way at all to access the interior unless it was one of the coopculture underground tours you'd specifically been asking about as those sell out within hours of being available. One other snag, though, would be if your chosen day was on the first Sunday of any month when Italian national museums are free: no tickets/reservations sold; colosseum to be avoided due to immense crowds and long, long queues.

The Colosseum is closed on May 1, December 25th and January 1st, and from 10 to 12 on Friday, 21th April 2017 so hopefully your chosen day isn't one of these. :O)

You don't mention when you're going to Rome but if you're going in April then you guide is partially correct but mostly wrong.

There is NEVER a time when the colosseum is sold out!! There may be times when it reaches capacity but they just hold the line until enough people have exited and then they let others inside.

If your "guide" was referring to the "underground tour" and you are going later than April then the guide is wrong again. The underground tours for April are sold out, which may be what the guide meant and if so then they are still partially correct. That doesn't mean that you can't enter the colosseum it just means you can't take that tour and enter the underground areas. There is a tour of the regular areas that is still available for April but you need to call to book that. If you are going later than April then there is no way for your guide to say the "underground" is sold out (if that's what she meant) because those tours haven't been offered yet.

Personally, I would ditch the guide and not just because of this bit of bad information. Getting to Rome is too easy to do on your own without paying someone to either drive you there or ride on the train with you there. If you want a guide for the city or a private guide for specific sites I would hire one who lives in Rome and meet them there. They can meet you at the train station and take you to specific sites in the city or just walk you around the city. You can either do that or just book specific sites yourself, online, and use official tours instead of expensive private ones.

Donna

Good advice from Donna: I don't see the need for a guide hired in Tuscany either. Use a Roman local if you think you need one at all.

"If your "guide" was referring to the "underground tour" and you are
going later than April then the guide is wrong again"

True: you didn't say when your trip was? Looking back at previous posts, it looks like you're going in June? Tickets for Coopculture underground tours for that month go on sale Monday, May 15th at 9:00 AM Rome time.