I'm looking for some advice on whether the amount of adults residing at my property (obviously this will be declared to my council as regards council tax) could affect my maternity benefits, working tax credits, child tax credits etc...
From what you have said, it appears you & your children are a separate household living in the same house. In that case they would not affect your tax credits or maternity benefits, but if you are getting housing & council tax benefit they would be treated as non-dependents & the amount of your benefit would be reduced by an amount depending on their income.
The benefits system is very complicated and whether or not there is any effect on your benefits from having adults living with you may depend greatly on who owns the house and what benefit(s) you are intending to claim. More specific information on your circumstances would be needed. If you aren't comfortable with sharing that, then it's better to seek help from the Citizens' Advice Bureau.