If Swift does not actually think the Irish people should eat their children, what does he think they should do?

I think that you can find the answer to this towards the end of the essay.  There, Swift starts talking about ideas that he does not want people to consider.  I think that these are the things he really wants people to do.  This is in the paragraph that starts

I can think of no one objection, that will possibly be raised against this proposal...

Swift goes on to list a bunch of ideas.  He talks about things like trying to get the people to use only things that are made in Ireland, or trying to get them to quit fighting amongst themselves.

It makes sense to me that his serious proposals would be the ones that he says should not be done -- after all, this is a very satirical essay.