Online Visa app - question about dependent passport info

We are completing the online visa app for my husband.  There is a section that asks about dependent children traveling with you and their passport numbers.  We have a 1 year old son and his passport application is still pending  (we submitted it 2 weeks ago) so I don't have a number - without a number we can't continue in the process online.

Any suggestions?  Would it bo ok to enter all 0's and then include an explanation in our cover letter?  I'm sure this must happen pretty often that both documents are pending at the same time.

Your son is a UK citizen and therefore is not a dependent in terms of your husband's visa. 

oh - so we don't need to mention him on the application?  It asks about dependent children and, I assumed, that included him.......

So this would just refer to if he or we had children that were not UK citizens?

I'm not sure, now I think a bit harder about it.  Maybe someone who moved with UKC children will be able to share some insight.