The first time I looked at secure frames, it threw me for a loop.
For a button that does an action, your button must inherit SecureActionButtonTemplate.
Next, you have a few attributes to set via ActionButton:SetAttribute() function.
First attribute is "type" which says what type of action click is involved. Since you are using an item, type must be item.
Button:SetAttribute("type","item");
Second is setting which item. That is done by two ways that you can find on
www.wowwiki.com's Secure Frames Overview.
There is an optional part to these attributes, adding prefixes and postfixes to type and secondary attribute. These prefixes and postfixes customize on which modifier and mouse click to do said action.
Also with the SecureActionButtonTemplate, you cannot change the OnClick handler. Instead, if you need something special to happen on a click, set the PreClick to have it occur before the OnClick handler or PostClick for after.