Dining table 2m or 2.20m... we are unsure

If a couple has 2 children and a couple with 2 children is a guest, you already need 8 chairs.

Can 3 people comfortably sit opposite each other at 240cm?

Does it have to be that the kids sit opposite each other? In my experience, the kids didn’t mind sitting at a separate coffee table... or kids go somewhere to play and grab a sausage on the go. Are you all such sticklers that you have to sit next to and opposite each other while eating? There’s finger food at sit-ins or standing parties, some sneak outside, if not it actually only takes place outside with more than 6 adults... Playing games is usually interactive or only done with 6 people. Guys, it just happens.

Are you all such squares that you have to sit next to and across from each other while eating?

It's a matter of the arrangement. At my parents' place, for larger groups, they simply put the ping pong table in the dining room and set the table well. It worked perfectly. Nowadays, everyone wants to be prepared for every situation. Up to 10 people, we fit nicely at the dining table; beyond that, we just improvise.

Table tennis table placed in the dining room

We always bring the patio table as well, then we reach 5 meters, but that is enough and there are too many people.

What kind of table do you have?

Solid oak table with legs at each end. Chairs without armrests. There is more than enough space for 3 people side by side and one person at each end. So in total 8 people. You could even extend it and thus expand to 10 people. But we have never needed that.

When you have such big parties, they rarely take place in the dining room, as has already been said!

Does it have to be that the kids have to sit opposite each other?
In my life, the kids never minded if they were allowed to sit at the separate sofa table... or kids just go somewhere to play and grab a sausage on the go.

Are you all such squares that you have to sit next to and opposite each other when eating? There is finger food at sit-ins or standing parties, some sneak outside, if it’s not actually happening with more than 6 adults only outside anyway... Playing games is usually interactive or is only done with 6.
People, it just happens.

Christmas, Easter, etc., does that ring a bell?
There’s no sausage to grab on the go and no finger food either.
That has nothing to do with being square but should actually be quite normal and part of upbringing. Everyone eats together at the table and the children can at least sit on their asses for this short amount of time. There is nothing more annoying than children running around during the meal and having to shove a handful of fries down their throats every time they pass by.
We’re also not in Woodstock or living in a commune where you have sit-ins and eat with your hands out of one bowl.

If there’s not enough space, there’s a separate kids’ table.

There are said to be parents who deliberately raise their children without religion. Church festivals are taboo there. It's always funny when atheism is elevated to a quasi-religion. But I am treading on thin ice with this topic...

On Topic:
When I suggested a extendable table, I received a slightly crazy-looking glare of anger, mixed with contempt and a little pity.
I don't know why, but some people apparently find that stupid.
But emotionally, I would tend to prefer a somewhat smaller table that can be expanded with additional tables if necessary, rather than having the big block in the way every day.