I've been in 10 groups, and had pretty much every role in them at some point.
I'm not sure I've found software that does all of that, but I do like GoBoKo for bookings and messaging - it'll also do things like tracking biennials and medicals if you want. Generally tech logs work best on paper, and pilots can look after their own logbooks without needing software help. Also make sure you've got an agreement now from everybody to any data being kept about them under the new GDPR regulations. Pretty much everybody I've seen does their finances in a spreadsheet - you could if you wish put that on something like a free Dropbox for everybody to update when they fly - but ensure everybody's IT friendly first.
I'd recommend having a trustee, chairman (last two often combined), maintenance member, treasurer, and consider having somebody responsible for organising regular cleaning as well. Have some mechanism for rotating those roles so that nobody feels all the work is dumped on them indefinitely - ideally nobody wants to do these jobs for more than about 3 years a time.
G