Great that you are doing this! We are a community volunteer group that does activities very much like what you are considering. We do two-hour hikes in publicly accessible natural settings, target 0-5 year olds (we welcome older siblings as well), and parents are with their children throughout. Our activities are open to the public. We do mostly Saturdays, so outside school time, but we have from time to time helped do hikes with HeadStart, Early HeadStart, and other preschools. A few things we have learned:
For most of our hikes we structure the time so that most of the time is child-initiated / free exploration/ play activity. We use an 'experiential learning' approach in which we follow the kids' lead as to interest, pacing, what to investigate more closely, etc. The kids' natural interests and the many things to explore and discover at the natural sites bring out wonderful learning and socializing results.
We take 5-10 minutes at the outset to get the group organized, remind everyone of basics like safety and 'parents/kids stay with your child/parents', and perhaps do a brief hands-on like making a snack or a simple explorer item. Then we spend most of the time in exploring and discovering (the experiential time), and 5-10 minutes at the end for 'processing' type discussion (leaders facilitate) and any loose ends.
We 'organizers'/ leaders pick a site (with parent input), make any arrangements necessary, and promote the hike. At the hike itself, we prompt the parents with a few ideas at the outset. We bring a few helpful tools, water, etc. During the activity both leaders and parents watch what the children do and scaffold gently onto those child-centered interests. Leaders coach parents to do so with their kids. Leaders help keep the group together.
Sometimes we offer a theme ('today let's think about…' things like colors/ shapes/ same-different/ things that move/ textures, etc. etc.) And we sometimes suggest a focusing activity (scavenger hunt, making rubbings, collecting a few leaves, or whatever) and bring materials for that (very simple tools and props, low-cost/ no-cost; we want the parents to be able to easily replicate those at home if they wish). But those are options, not a requirement. Most families do the suggested activities at least a little, but many of them move on to other things that interest them. Walking along and looking/ poking/ wondering about things makes up most of the hike time.
Favorite activities for our groups have been
Others have shared great resources. I'd add the books by Joseph Cornell - great activities.Hope the ideas are helpful!
Sam CorneliusKids Outdoors OtsegoGaylord, Michigan