What kind of work are you pursuing? You can have more than one resume for each field you want to apply. Also, when submitting resumes online, make the job descriptions from your past as detailed as possible. The idea that resumes need to be one page is only the rule for face-to-face interviews. The web changed this little rule since you left the workforce. The recruiters now input key words that scan the online resumes for matches. You want to be matched, so a 2-3 page resume is the best way to accomplish this. Your past experiences will bridge to the current market needs unless the market changed somehow. This is really up to whichever field you pursue, so be honest with yourself about where you need to shore up your experiences with online courses or networking into the field for some insider tips.
As far as the break in your experience for family, communicating this is your personal preference. My personal preference is to leave it blank, no explanation on the resume. Let your past experience and education get you the interview, then speak objectively about the work you accomplished at home. I am not a fan of the "SAHM is a project manager role" thinking... there is so much more flexibility in our roles as SAHMs than in the corporate world, no matter what level of management we could be. Some employers will accept your choice to stay at home as a reasonable choice, but they may look at you as being outdated. You'll have to demonstrate that you are with the times somehow. If the place is going to be critical of your choice to stay at home with your family, is that the kind of place that is going to support you in the long run with your personal needs (i.e. time off, medical plans that support families, etc.)?
I am really interested to see what people have to say in response to your question because I plan to enter the workforce within the next 12 months. It's exciting for us! Good luck to you.