I'm probably not the best person to answer this as I haven't looked into this much (as I already know that I am not going to the bracelet related evening events), but to my understanding the evening events are all clubbing events, and if you aren't a huge party goer (and only plan to go to one or two), it might be best to hold back on getting the bracelet as you can just buy an entrance ticket on the day depending on what event you want (or don't want) to attend. I think the bracelet does mean you don't have to queu for as long though, so there is that too.
A lot of student societies also have evening events going on throughout welcome week, so if partying isn't your scene there is likely something else going on you could attend instead, like a film screening or pub quiz etc which you won't need the bracelet for.