I don't run a home daycare but as a mom who requires daycare I would advise you to honour your long-standing promise to your friend who is in need. If she has been depending on you, and then you say no at the last minute then what will that mean to your friendship? How will she be able to arrange daycare at the last minute? Were you her only option or does she have other dhild-care options?
Leaving your kid after mat leave is stressful enough without having to frantically find a trustworthy caregiver without having the time to do the due diligence, research and site visits.
Since you don't NEED the money and you have promised to take care of a few kids, then I would say no to the ones who you most recently said yes to. Explain to those friends that you may have been a little too enthusiastic in your response but you simply cannot handle so many kids at one time.
Your 17 month-old son can only benefit from interaction with other kids -- his age and older. He'll learn to share and communicate and interact. All valuable social skills.
The important thing is: Can you handle giving care to multiples of children. If you can, then go for it but know your limits, legally if you are getting paid and personally (in terms of physical space and your energy level).
Hope this helps.
