I think it depends on what work experience you have before you stayed out to mind your children.
If you have very high level work experience, employers might wonder how you got the previous jobs with no maths degree.
On the other hand, if your experience prior to having children was at a reasonably low/medium level, then you could leave out the Msc. You could put in a degree, as lots of people have degrees nowadays. There are lots of people nowadays who have a degree, and who don't have a high flying job so leaving in the degree would do you no harm.
If you have lots of very good work experience, you may need to dumb this down also, as otherwise agencies may try to place you in a demanding role.
I know it is easier to get more lower level jobs if you have less qualifications and experience. If you do not dumb down your CV you could be left without a job, as the employers would think that you will leave to pursue a more challenging role (despite what you say in the interview about not wanting a demanding role). I know it is frightening, but the more highly qualified you are, the harder it can be to get work, as employers are afraid to take you, they want someone who will stay with the company.