Should you invite children you don’t really know to wedding?

[Hippopotomum]

I need opinions. Weddings are always hard, and I’m a push over so I need to be told what to do by outsiders 😂

We’re getting married next year.
DP’s got a family member who has a partner and a toddler together - she also has an older child (near teen) from another man. We’ve met her once briefly.. and the time that we did meet her, her mum was quite rude to our friends.

But they’re together and they have a child so we’ve invited them and their child.. but not the older child? We’re really tight on numbers and both me and DP have had to cut out some family and friends that we would like to have been there to fit in more ‘necessary’ family.

They sent us a message to say they (including older child) will be attending the wedding. I’m not sure if they just haven’t read the invite.. or whether they’re making a point that they want her to be invited.. but we can’t really afford or justify inviting the child we don’t know and have met once. Is that wrong? Should we just invite her, if we invite her then I feel like we also have to invite DP’s brother’s step-children and it’s having a domino effect and we’re going to be over on numbers and struggling to afford to feed them.

We obviously don’t want to be rude, and we don’t want to cause any drama - So should we just invite them and deal with the stress? Or if not, how on earth do we politely say shes not invited?!

Depends on the wedding, surely? Mine wasn't formal, didn't have waiters carrying trays and didn't have risqué speeches. There was alcohol but lots of family events have alcohol.
Not all weddings are boring formulaic overpriced stately home affairs.
And I've seen plenty of children at those type of weddings anyway and it's been lovely.
Some people are just intolerant of other people's children and it shows.

OP wants kids at her wedding and that's fine. But she needs to invite all the children, you can't pick and choose if their parents are invited!

I agree @howaboutchocolate
I've never been to a wedding that I would say was an unsuitable occasion for children, and to be honest I'd probably consider such any that were, unsuitable for me too!
People are different, and weddings are different. Saying "weddings are unsuitable for children" is a bit like saying "restaurants are unsuitable for children". Some are, some aren't. Depends on the event, and the child.
The average wedding service is shorter than the Sunday morning services that my children have been going their whole lives so they never had any difficulty keeping quiet in a wedding. But at the other end of the spectrum, asking a toddler who's never been in Church before to sit still though say a Catholic wedding that included a full mass as well as the wedding ceremony and lasts ages would be totally unreasonable. Likewise my wedding started at lunchtime and was over by 6pm - fine for kids of most ages. Taking a child to a wedding with a reception that goes on to 2am, probably not fine. You just can't generalise and it's a matter of individual choice.