Yes you may change it just a day before to get the ITA and in 24hrs the golden mail will be in your inbox.
Lemme put some light in it with no offense meant my dear friend. How you think you will convince the case officer and the visa officer that why you are not accompanying your spouse and children if you have? Ofcourse you're not gunna say that just because you wanted your CRS to be above the threshold, you're not accompanying your spouse........ knock knock, that'll be a red flag.
Now let's suppose, you come out with any reason apart from the above one, it'll be a fake one and they will get you in a jiffy.
And if above points mentioned, you get thru, you will sponsor your wife and children if you have, they will never be entitled for govt benefits.
So think before you exclude your spouse from the application as it sounds easy to get the ITA but mate, trust me on it, it's even harder to remove the RR forever from application for not accompanying your spouse.