Can someone suggest me if I have to include my sons name and have to pay 2389£
1) I am on tier 2 general visa. Having work permit.
2) I have my wife visa tier 2 dependent.
3) we have 15 months old baby born in the U.K.
4) we are going to complete 5 years by 2021-April.
5) I have my employer reference letter(going to provide valid proof)
6) We have completed our English language tests & Life in the U.K. test.
7) Now the only thing left to apply ILR in the month of March-2021 (28 days before).

Now my concern/doubt is do I need to include my sons name as a dependent while I am applying for U.K. ILR (though he was born here) ?
If so I have to pay extra 2389£ for him?
OR
I don’t have to include his name and once we have my ILR status completed, we can apply for his U.K. citizenship? So he can be a citizen?
Please advise..
Thanks
Durga.P