Pre-K is an excellent time to introduce to a child learning through many senses
(Known as multi-sensory approach). For example, say that your child likes bugs. You can read books about bugs, go outside and count the different kinds of bugs they see by hiking and then create an activity (such as making a caterpillar) from easy to find arts and craft items. The key to keeping a child's interest at this age is to make it so that they "direct" which topics they want to explore. Try and have a list that can be displayed and cross off each topic when he/she feels they are ready to move on to the next.
This is also a great time in a child's life to introduce music, dance and the visual arts. Field trips to museums, family made scavenger hunts with adult supervision, visiting local parks and family centered concerts are all ways for a child to learn and have fun! Also, this kind of learning tends to be very enjoyable for adults, as well!
The arts and crafts projects get creative, and there are various educational activities that build skills like number recognition and sorting.
Phyiscal activities can be the most enjoyable though. A simple trip to the park can give great exercise. Climbing steps up a slide, swinging, or playing tag with other kids. If there's not a park nearby bring a ball to an open area and kick it around. This will help build motor skills as well as strength.
I do not teach pre-k, but I do teach children with autism in the kinder-1st grade level. I have found it to be the easiest to choose themes and then start my internet research from there. There are a ton of great free websites out there! Good luck!