TWA... from your posts I know how much you care for those kids...
Remember to place them in the hands of HP/God/whatever you want to call it....
Also, remember when these kids grow up (or now for the 14th year old) if they choose to they can keep in touch with you... even if they stay with their mom, they will grow up and would probably want you as part of their lives... even if its only by email for now if needed...
All the best.