Horti if you like any sort of craft be it sewing ,knitting ,painting etc. Either Google groups in your area or your local library is a good source of information.
As for exercise sit fit classes are fun. But don't think they are an easy option compared to a gym or pilates they aren't. I go to one in my local church . It's not run by the church our instructor rents the room I am the youngest in the class at 65 oldest member 91. Our instructor is in her early 60's so she doesn't go easy on us. But always says if it hurts stop but you should feel your body working. We sit down for some exercises and stand behind our chair for others . We use weights and resistance bands.£5 for a hour .Not matter how much pain I am in or how wobbly I still go because it's helps strengthen my limbs and helps with my balance.
I go to a mixed media craft group. Doesn't cost anything for 2 hours . We have a box with tea etc, and biscuits when anyone notices we are getting low on things they buy it. I bake some goodies every 2 weeks to take . Age range late 20's to mid 80's.
The library has a lot of different groups. My exercise instructor does a class there .
I only go to daytime events. I look after my grandsons when needed but my daughter asks well in advance. But if it was on my days I do classes I would just take them with me. My daughter takes her youngest with her to her exercise class and the oldest as well when it's school hols.
Just because you look after grandchildren you don't have to stay in. You say you have health problems so do I and members of my exercise and craft group do to. But the only limit to what you do is what you put on yourself.