Yes, the dates of when you worked are very crucial to your resume. List all of the jobs with all of the dates that you have had in your resume. You should state that you were a stay at home mother for 8 years.
You really don't need to elaborate too much on why you didn't work for 8 years considering that being a mother is a full time job and the company will understand.
The best information remains, the truth , the whole truth and nothing but the truth. Do not attempt to explain it on the resume, that is the job of an interview. Every employer understands that you took time off to have kids and get them into school.
The real question becomes why are you back in the work force. Very gently suggest its time to get back in the market and make some money. Try not to suggest you NEED the cash or are only working until (insert reason here).
A good HR person will see through any resume avoidance maneuvers. Best to just list the dates and facts. "I am committed to working now, kids are full time in school " This is the for a cover letter and says it all.
No more need to explain.