Usually, about once a week, I arrange to meet up with my daughter in the park when she takes her 10-year old for his exercise. We never come close to each other, probably at least 3 metres apart at all time, but she walks, lad runs, and I trundle (mobility scooter) round the park, admire the flowers, look at the fist and watch the birds and squirrels.
In one, particularly quiet area my daughter will sit down on a bench for 15 whilst the boy goes off for a really active run around. I sit on my scooter a goo distance from her. The 10-year old understands that he must also stay well away from me
Must say, I really look forward to these strange meet-ups and the chat we can have. Living by myself (which I thoroughly enjoy in normal times), just being able to chat in this way is so lovely.
More difficult with a 18 month old child. Perhaps you should go by yourself and have this arrangement with your Mum, but point out to her that you must remain well apart at all times, and it can only be done about once a week.
Not surprised the Mum is so depressed with everything that is happening. Have always maintained that whereas most people will survive this virus, many of those will end up with severe on-going mental health issues.