Group created by old batchmates

We, old college batch mates met and create a WhatsApp group.  We are planning to have a get-together. Also in mind to collect/accumulate some funds to help our co-members, who are financially not sound or to give gifts to appreciate the member's children or our college children who securing highest marks.   Do we require to register the group as a club or association with any legal authority to collect donations etc?  Do we require to get an exemption from Income tax to collect such donations etc?  Pls, advise.