Tisha B'Av activities

Other posts still swirling in the background, but for now...

Interesting that one is not allowed to learn Torah on Ticha B'Av because it is a joyous activity, and in fact should be the epitome of our joy. Yet I don't think (please correct me if I'm wrong) that other potentially joyous mitzvot are off-limits. This afternoon my mother and I visited an elderly homebound woman who we know from our long membership, years ago, to a certain Conservative shul, and from there we went to the hospital to visit our neighbor who gave birth on Shabbat to a beautiful baby girl. Is there any discussion of the propriety of such activities on our national day of mourning? Perhaps there's an unstated (or stated?) hope that performance of mitzvot ben adam l'chavero will continue unabated and somehow catch up with our balance of sinat chinam that has prevented the Beit Hamikdash from yet being rebuilt?