I have studied early childhood for many years, and honestly, even theme weeks rub me the wrong way. While it is relevant to study the natural cycle of life and seasons, theme weeks often remove the child from natural occurring learning experiences. While there are many themes that children relate to, like animals- cats/dogs, barnyard animals etc, that is different than planning a week around a theme, like apples. I am not trying to discourage you choosing to base lesson plans on themes, but emergent curriculum that comes from the child and their family is far more relevant to young children than learning about apples because it is A week. This isn't to say that you can't do a letter of the week or some such activity, but try to relate it to the child and their interests.
As the daycare provider you can offer experiences, such as investigating plants, let the kids explore the parts of the plant, take a part a flower, plant etc. Math, science and reading can be part of these experiences. The children could count the number of seeds you plant, measure the plant as it grows, observe the plant as it changes etc. This is all math.
If you are just starting out, the Creative Curriculum really is a good source, and I highly recommend it to people just starting their own daycare or preschool. Children who are actively involved in play, that move freely within a space choosing activities that are developmentally appropriate and interesting to them will develop the skills they need for preschool and school readiness.
You might want to consider joining NAEYC, National Association for the Education of Children, Zero to Three or another early childhood organization. Magda Gerber is another name I recommend, as well as Maria Montessori. (Many of Magda's ideas work well with AP)