From my own experiences I'd echo Saracen's post, esp last two paragraphs.
Knowing what works for you or not, or may be deal breaking clashing points could save you getting into awkward situations later.
(ie discovering grouped parents who didn't believe in telling their or another's children off for unpleasent behaviour to others vs me not believing in not, or knowing it to be seen as desirable, is one I fell at the first hurdle with, just in attending a social group.)
I've only previously known one set of parents belonging to a full on education 'co-op' and the mum's perceptions of it did sound a bit marshalled and fraught to me tbh, but know lots of individuals happily skill swapping (inc caring) in twos and threes, and net working as part of h.e. mutual support and back scratching.
(There are a few fee charging circus skills, and arts performers popularised by H.edders, so I’m sure there’s a possible ‘market’ for skill exchanging.)
Having said that, I’m aware of two new London one's starting up currently. One's a group of estate based parents who've recently lost their local school and are unhappy about it, and are grouping and sharing responsibilities for mutual support against common misconceptions. the other's a high flying group looking to skill swap, who seem (I could be wrong) to be veiled self-restricting to quite highly educated parents with reasonable finances.
BTW being 'rubbish' at something, only matters if you're under the impression that you should be handing down your knowledge, or are unable to access resources. Being openly unknowledgeable seeking to learn, and allowing your children to accelerate past you as you tackle things together, can be as good a way of creating independant learners and helping them get educated to a high standard, as any.