Waiting after international flight before clearing customs

Do not try this at home (airport actually)

If you wait 3 hours before going to claim your baggage your baggage will already have been picked up by the lost baggage team and a large group waiting without collecting their bags will trigger a security scare.

Its not so much about some people wandering around in the lounge as it is about let's say 25 unclaimed bags. I have not been to Chicago O'Hare but I have not actually seen any restaurants or decent sitting areas on any international airport for arriving passengers before they clear immigration.

If we clear customs on arrival we will be left waiting in the area with no restaurants and without a decent waiting area

On Arrivals you do not get access to that decent waiting area with restaurants (According to a comment below, this seems possible at many European Airports). Generally you won't really have access to those restaurants that the departing passengers can go to. Actually You're more likely to find a coffee shop or a restaurant after clearing the formalities.

I have arrived at Chicago O'Hare (ORD) on international flights before. After landing at ORD, passengers deplane and enter a international arrivals terminal. There are no amenities in this terminal other than bathrooms/restrooms. Instead you are expected to move through the terminal toward the US Custom and Border Protection (CBP) checkpoint.

1. You will need to clear an immigration check: i.e, present your passport, visa, etc.
2. There is a series of baggage claims, where you will pick up your luggage.
3. You will need to clear customs, i.e., declare any goods.
4. Exit the checkpoint and enter the arrivals terminal. This is where non-flyers may meet their family/party when the exit the checkpoint.

There is nothing to prevent you from waiting in between any of these steps. There is just nothing to do in the this international arrivals terminal. (Other than visit the bathroom.)

References: https://www.flychicago.com/ohare/myflight/international/pages/default.aspx

I am making the assumption that you and your party are not received preclearance before flying to ORD.

Your thought seems to be that your group will wait at one of the numerous restaurants, cafes or seating areas universally found in airports, then your entire group goes through Customs together.

First, it's a lot faster to get your 9 stragglers through Immigration and Customs than your whole brood. Any one of them can have a "problem" with a multi-hour grinder of detention and secondary interviews. That's far more likely with 40 people than with 9. So you are better off moving the bulk of your tour through ASAP, that way if one has a problem, they're likely to be done when the 9 arrive.

Second, you might not both be arriving the same way! Some airports have preclearance, where flyers clear customs/immigration inside a "USA control zone" in a foreign country's airport; that plane won't go through C&I again, and will gate elsewhere, probably domestic terminals. Those terminals are quite some distance apart. And the mere fact of the plane departing a preclearance-capable airport does not guarantee it will be pre-cleared.

Third, as others have said, for non-precleared flights, the pre-Customs area does not have restaurants and cafes. It's designed to efficiently herd you toward immigration, and expose stragglers. Trying to linger there will raise suspicion. People do naughty things in this area.