Your question is two fold and I shall try to answer both.
First…there are two ways to go about increasing the share capital and allotting shares to your wife and children. This can be done either by the transfer from you of existing shares or else by increasing the company’s share capital and allotting these to the wife and children.
The first option would be a private agreement between you and the wife and children and no cash need be injected into the company.
For the second option, since the company is issuing new shares, there must be some form of compensation. In your case you stated that you did not wish to inject cash. Then perhaps these shares can be paid for by converting some existing loan that you have with your company. This would first need to be loaned or granted to the wife and children through a private agreement and then capitalized into share capital.
To retain control of the company affairs, there are various ways to go about it. Such include the allocation of preference shares to the children or to a different class of ordinary shares with non-voting rights.