I mean, we love ours but we would never just assume they were invited to a party unless it was indicated in the invitation.
If you address it to "The Bear Family" or you list the kids by name then we assume they are welcome. If you address it to Mr and Mrs Bear or Harmless plus one then we will be getting a sitter.
Back in the day, my parents went to and gave party’s adults only. They needed to get away from us monsters once a week or so.