Self employed

A follow up question:

we have been working on the book together, with quite some cost, not published yet. 
is it possible to deduct the expenses?
is it a good idea to report it as a “hobby”, or a new business?


in TurboTax Home and Business desktop version, I tried to make it a “new business“, TT asks if me or spouse is doing the business, there is no option of making the child business owner (under 14yo).

any advice? Bless!