A lot will depend on the child's age and understanding of what is going on. If the child can't even process why someone is fighting their mother, then no. If you must have a child watch a fight, then have an adult with them to explain/screen when needed. Every sporting activity has potential for injury. Few would likely forbid their child from watching mommy play soccer, but she could have her ankle shattered by a rough tackle in front of them.
An older child closer to 18 is likely to have less issues with seeing a parent in a combat sport, but temperament is still a factor. And don't be shocked if forbidding them just makes them more curious. And let's face it, some of the things that have happened to people at a sporting events most adults have had trouble dealing with. So its a judgement call based on the temperament and age of the child and the risk you are facing.
The above comments are for organized, sanctioned sports events. Private matches I would be very leery of exposing children to because of less regulation and more chance of injury/things getting out of hand. And the chance of sexual content in a match one likely does not want their kids involved with. Plus..how well do you really know the couple you are fighting? Having your children at a fetish match with a strange couple could be REALLY bad news (not a good time to learn your opponent's hubby likes them young ). And it doesn't seem like responsible parenting to save on a babysitter by bringing your kids to your fetish meet up
