Whereas we (UK Open Mic) are happy to have performers, or audience, of any age, it is entirely the venue's decision on any given night as to whether they allow families / kids / children.
Additionally, if under 18s are allowed, it maybe only until a certain time and only if accompanied by an adult.
The best thing to do is call and check with the individual venue you're thinking of attending that week; it is entirely up to them and we don't want you travelling for nothing! (especially if you have kids in tow!).