Horse riding sounds fair - it is an expensive activity wherever you go. I know somewhere where it costs £25 for a child to sit on a pony and by led by someone on foot, and that is for 30 minutes. We pay £35 for an hour proper lesson.
I'm not sure I'd pay for someone to show me round Botanical garden, unless I was an enthusiast. I'd probably enjoy looking at the flowers and go for a cup of tea and a piece of cake