You should probably use a multisignature wallet. That way nobody can spend money without the group's approval.
Do you have example of one?
I'd recommend Electrum which support multi-signature wallet/address. They also have short documentation at
http://docs.electrum.org/en/latest/multisig.htmlWeb services such as
https://coinb.in/#newMultiSig also offer similar features, even though i recommend to download the software and run it offline.