just be open and honest with them but you need to do some research first... call up tinies nanny agency and explain your work load and ask them what the range of expected pay is. if yours is differnet then are in a good position to negotiate. then say you'd love to keep working with them but feel that the original job spec has slightly changed and that you've spoken to an agency, and they've given you a guide salaray range of X-Y / hour also, youre in a different year, so you should expect an in-line with inflation rise anyway -that's what we give our nanny each year.