Hi René,
I have worked in Marketing & Advertising for over 20 years. As I read through your post, a few thoughts came to mind.
If you have a computer, you can probably put together some SIMPLE, TASTEFUL business cards using a template from a page layout program on your system. The same goes for a flyer. You can quickly, cheaply get together some marketing materials.
First, keep in mind that people looking on Craig's List are generally looking for a bargain. Your cooking service is more like a luxury item. Let's face it, times are tough and people in the same boat are looking to SAVE money, not add cost.
That said, I still think your idea is a good O.. You just need to reach a more "upscale" or "specialized" audience with your service. If your goal is to recruit four families that you think will use your service consistently, then you'll have to reach out to a more affluent audience of families. Personally, I would imagine that your ideal target "client" would be a double income coupple with children. Post info at daycares! Start with the very basic--TELL everyone you know about your cooking interest and your business. Then SHOW your stuff! I like the idea of hosting an informal get-together to let people sample your food.
Think for a moment that the above scenario may not be the ideal situation. I know that in your head, this idea may look like "four families I am cooking meals for every week", but consider thinking outside the box for a moment.
Most importantly, you should look for a niche in your area that is not being met.
Perhaps you could offer a "new-mom package" that would provide 8 full meals along with a light grocery order (milk, cheese, bread, fruit, etc.) that would last a new mom about 2 weeks when she gets home from the hospital. Place cards/flyers at baby-oriented businesses in your area or tack a card up at local OB/GYN offices.
OR
Maybe you can market to baby boomers caring for an elderly parent(s) that you will provide their parent with a few frozen meals for the freezer every week. Now THAT, in my opinion would be an awesome niche to get into, as so many 30-50 yr olds age caring for their parents while working full time. Place your card on bulletin boards where busy, working people go--the market, beauty salons, the gym, office buildings.
The key to successful marketing is not to just throw "stuff" at a wall & hope some of it sticks, but to streamline your "voice" to reach those who need to hear it.
I wish you the best of luck and I hope some of these tips may work for you.