What's the difference between the "meaning of an action" and the "purpose of an action"? ...I feel actions are interpreted through their purpose. I don't think "to invent a meaning" makes any sense when applied to "actions" unless you are including the possible purpose/motivation of the action as part of what you are inventing for it.
Unless what you mean by "meaning" is "consequence".. but in that case, you are not "inventing" it.. consequences do happen, they are factual.. at most you can interpret the consequence of the action, in the sense of viewing them through different moral perspectives, but even this would be heavily determined by "purpose", since all moral frameworks judge reality based on a purpose/goal/ideal.
I feel the popular concept of "the meaning of life" is equivalent to "the purpose of life".. and talking about "what should we do?" as the "only choice that matters" does implicitly set the weight on meaning/purpose, since that's what directs our choices.