To start on the right foot, I am a pretty useless and rather clueless gardener!
My garden is gravel (was when I moved in so not my doing) but it wasn’t done particularly well. Around the edge in the soil are a few weeds and prickly things which I am trying to dig out, and ultimately need to kill off. I also have an area of gravel where grass is coming up (hence my “not done well” comment!)
Trouble is, there’s a few cats from around the area that play in my garden! I only know where one comes from! I need to put down quite a lot of weed killer but don’t want to be responsible for the death of a beloved family pet! 
Any advice on how to tackle this safely or am I worrying for nothing?