While I agree that with "atlanta tax expert" about the $50 comment - I don't with the other. Just because your return has been accpeted by the IRS DOES NOT MEAN it has been reviewed. You are not technically "safe" from audit until 4 years after your file date.
I would definitely ammend your return (and don't forget to do it for state as well). If you are taking away the child care expense and adding mortgage interest - it should be relatively easy and not take very long - and hey - you may just get a refund. Just use amended tax form that can be found on irs.gov.
I would also take a look at your past returns as well. If this "tax professional" missed something as basic as mortgage interest - he probably missed other things as well. Remember - you can go back 4 years. I believe a couple of the mainstream tax companies will review past years returns for a smaller fee if you aren't interested in doing it yourself.
Hope this helps!
Tax auditor in CA :)