There ARE events like that, but often it is hard to travel to them when you have DC with SN's, so more regional or even local things are often more helpful.
For someone like me, it is hard enough to cope with my dc on a 1hr train journey to London, I wouldn't attempt it lightly, as with 4 dc, one a baby in a pram, two with diagnosed Autism, one in the process of a diagnosis, me with epilepsy, and being a Lone Parent thus having to possibly try to cope with 2/3 meltdowns AND a baby all at once alone, even the 'local' groups are almost impossible for me to access.
The 'local' group for parents of children on the Autistic Spectrum is an hours' bus ride away, across the town, and I haven't been more than once a year because it is so difficult for me to access.
It's VERY isolating, and there is no help available for me to access to GET me there quicker.
I can't access the Epilepsy support group as it is in the evening AND is impossible to get HOME from by public transport, as it is two buses there, and the last bus from the group to the town centre leaves 30 minutes BEFORE the end of the 2 hr support group.
I can't access the support group for Autism, as the hour bus journey each way isn't feasible with all 4 dc when I am alone.
I can't access the LD's group for DD because the teenagers one runs from 7pm-9pm on a school night, and she would get back home too late by public transport when she has school the next day.
IME, All the support groups seem to assume that everyone has a car. Or has a partner with a car that can drive them around. If you don't, then you are screwed for support.
The SN crowd on here ARE my only support with my issues - the only other people I know in RL that also have SN DC have been dealing with it for a lot less time than me, and look to ME for the support IYSWIM.