I came across the Field Studies Council when I was doing an Open University course, and they organised the residential and day field studies trips. When I visited their website, I found out that they do trips for kids and families as well. There are various types: holiday camps where you leave your child for the day, or family days where you attend together.
These aren’t specifically aimed at home educators, so they’re often weekend or holiday time, but they are a great chance to get outdoors and do some activities in the woods or fields, and learn something as you go. The holiday camps tend to be general forest-school-type activities – lighting fires, making mud pies, etc. Other days can be more detailed, focusing on specific topics like moths, invertebrates, etc.
Several of the courses also include arts practice: drawing or crafts.
Not all courses are suitable for all ages: please check.