Welcome and Congratulations. As you have come out to yourself and your partner the hardest part is over.
How to approach the situation with your children is always a bit tough until you actually do it, even when they are adults. At 4 though, your daughter is living in a magical world where things change into something else all the time, so I think she can cope. There are lots of single mothers out there doing a great job too, as well as same sex couples, so don't put yourself down.
It's understandable that you have become a bit self-obsessed, we all do at first, as we are trying to reinvent ourselves on the run. It will pass, especially if you have a good Gender Therapist who can help you ask yourself the right questions.
Are there any options for tertiary study building on your trade qualifications? That might be a good place to look for career options.
Whatever happens, remember you have a really big family here.
Karen.