It is definately worth mentioning some things you have seen/done - but you need to try and make them relevant to your and your PS.
Putting that you did 2 weeks as xx small animal surgery and observed spays, castrates, dentals and so on doesn't do much other than show you have stood there and watched. Instead you need to show what you have learnt/benefitted from things. So, for example the case you mention above, you could include and explain how it made you aware of the ethical dilemmas vets can have when faced with a case to treat that has a history to it, but how your focus is on the animal etc. Equally, they might be a case that has shown you the need for effective team work during an operation and careful liason with owners for some reason etc.
What you need to make sure with your PS is that everything is in there for a reason - whether it is sports clubs, the fact that you read whatever journal, have seen a particular operation - don't just list random points, why do you do this, how do you benefit, and most importantly, why is this relevent to your vet application?