My question is on the grammatical correctness of the following sentence with regard to the form of the verb 'join':
The plan is that the group join the party.
Other sentences that I think represent the same issue (regarding the verbs sing, consider, maintain) are:
I ask that the choir sing at the banquet.
The advice is that the committee consider the alternative.
The advisor recommends that the firm maintain its involvement.
In each of these above sentences I attempt to make a command (do this: join, sing, consider, maintain) but to a third person subject (as though not speaking directly to the group/choir/committee/firm). Microsoft Word's grammar features suggest correction to me from 'join' to 'joins'. Is it grammatically incorrect as I have written it?
Basically I am trying to write a proposal in which I implore a recommendation. I essentially want to say, imperatively, "do this", but more gently/politely or in a more passive tone. I picked to say "that the group join" because to me it's as though I am saying "that the group will join" or "that the group would join", but I don't want to write that out to avoid being too pushy (saying that it 'will' do as I say) nor too nonpersuasive (telling them that they 'would' do as I say, if they feel like it.. or not.. whatever..). Nor do I want to say "the plan is that the group joins" because my purpose is to recommend (propose) for the group to carry out the action, in the future.
What's a correct word choice or conjugation here? What's the best tense for the sentence?