As pp says make 'stay at home mum' a positive statment. Don't forget that it gives you great organisational skills along with people skills, diplomancy, multi tasking. Make sure you put these skills at the top of your CV, as I was always told, if they like what is on page one they will turn over the page for personal details so catch their eye. You have previous experience - so page 1 - skills and previous experience, page 2 - education and personal details. Don't just repeat your CV on your cover letter, use it to point out that you are keen to return to work, with them. If you can apply in person rather than just by post, that way the manager gets to see you looking 'together' and has an idea of what they will get rather than assuming that you are a frazzled parent.
Good luck