best "skip the line" tours

Kathryn, it would help if you could fill us in on your interests - no sense sending you to attractions you don't care to see - and if these tours are for your FULL group of 11 + a toddler and infant? That's an important detail as, to accommodate all of you, you may need to book a private guide.

As well, "skip the line" is merely a marketing plot to cause visitors to think they're getting something special when very often advance, timed-entry tickets, when available, booked on one's own provide the exact same benefit.

Yes, we have a total of 11 adults and 2 very young children. We would like to see the "top" attractions (Louvre, Eiffel Tower, Arc de Triomphe, bus tour of the city, and a River Seine cruise ( the cruise, if you think it's a "must.")
I definitely think a tour of the Louvre is important so that we see the most important art - and not miss it!
Thanks! I look forward to your suggestions!

Gratuitous advice: with a group this size I would be planning to split up into small groups for many of the days --- there is no way that 11 adults are going to all be fascinated by the same things and no way 11 adults are going to want to be weighed down by 2 small kids in a herd every day.. 3 groups doing different things -- and getting timed tickets for those attractions for line access and then meeting for dinner will likely transform the quality of your trip.

skip the line is a misnomer that makes you purchase overpriced tours from Viator, etc.

All that you mention [Louvre, Eiffel Tower, Arc de Triomphe, bus tour of the city, and a River Seine cruise ( the cruise, if you think it's a "must.")] have security - you're not skipping that.

You can purchase Louvre, Arc, and ET tix all in advance. River cruise, no need you can walk up to your preferred vendor and purchase then (or online, there's usually a savings).

Buy directly from the actual site, nothing via Tripadvisor, Viator, etc.

Honestly? A group your size would benefit from the services of an experienced travel agent: it's going to be really difficult to book 11 adults at one time into the Eiffel, into the Louvre or others of Paris' popular attractions. Even 11 on the same bus tour could be a challenge, and meals together will be its own issue. I'd follow the good advice to split up into smaller groups to ease some of the complexities, especially as the youngest may only be able to handle so much.

You don't need a tour for the Arc de Triomphe but you do need to be able to climb 15 flights of steps. Buy tickets here:
https://tickets.monuments-nationaux.fr/en-GB/families?site=2032863779450400197

Louvre: see the tours the museum offers:
https://www.louvre.fr/en/what-s-on/guided-tours

Not a fan of bus tours so no suggestions there; maybe someone else has one?
Oh, and as mentioned above, if an attraction has a security check queue - as many do these days - NO one is able to bypass those.

The Louvre has a self-guided tour posted on their webpage, so you don't need to pay extra for that. Download it on your phones or print out the steps (it includes directions) and have at it.

Private guides are not allowed to take groups as large as yours around the Louvre. The exception is a multi day organized tour whose company has made the arrangements.
However, the Louvre does offer a few highlight tours in English. If you watch the website closely, you may be able to purchase tickets for those who want the tour.

Is everyone on board with doing everything together? The parents of the two young ones might enjoy a more leisurely Paris experience while a group of 3-4 are the see it all, see everything! And the others are more the plan a couple of things and see what falls into place.

Is there a reason they aren’t planning their own time in Paris?

I understand wanting to have more specifics about WHERE and HOW, but then disseminate the info to all concerned and let them plan their days. I’m sure there is more to this than 11 adults and 2 young ones trying to do everything together., which I see as a bit of a logistical nightmare due to transport, et al.

And, I agree, getting together at the end of the day and sharing all the different adventures each group/individual had during their day would be so much fun and educational.