There are some career counselling services that will also give you an aptitude type test that identifies strengths and weaknesses and may point you in a direction you never thought of.

To be your own boss you could look at something like Usborne books, discovery toys, etc that would allow you to run it as you want, put your childcare/therapy skills to use and eventually have a downline to oversee. If you are undecided on the things at the end of your post this might be a good option in that you can move it with you, slack off with a new baby, etc.

Are there other things you had an interest in when younger that your own children might be getting into that you could get involved in but from a work standpoint not just volunteer - skating, a craft, etc.

Is there the option to open a therapy business but be the administrator rather than one of the workers - or something related - always a need for respite workers.

Many charities need people who can help with fundraising especially.