Hello Providence, you have a little work to do.
First, download:
http://www.irs.gov/pub/irs-pdf/p54.pdf
And read it carefully. You will find it very helpful.
Now, find yourself a professional tax preparer who can deal with US taxation because you have several years you must deal with. I can recommend Liz Zitzow:
[email protected]
You will owe no self employment tax on your business income because of the "totalization agreement" between the US and the UK.
Moreover, UK tax being generally higher than US tax I doubt you will owe anything to the US.
Depending on your income and the age of the children, you may be entitled to the Child Tax Credit. Be sure you do not use form 2555 but use instead the Foreign Tax Credit.
Most likely you will file "Head of Household" unless your husband wishes to be taxed on his worldwide income.