It's entirely up to you if you want to reschedule your test. There are no pros but the cons are further delay in your application and more stress etc. If you have got the invitation letter than why not postponed the vacation that makes more sense to me.
I would. And I have. I had a vacation plans all set when I got my test invite letter which informed me of my test date falling in the middle of my planned vacation. I cancelled my vacation.
People have successfully rescheduled however. The cons of this is that the the date can get pushed back by a few months. If you don't care about waiting a few extra months, then you can call them and give it a try and see if CIC lets you reshecule.
I got given a test date last year that was to be in the middle of a trip with my dad, that we'd planned and booked months in advance, to go and fulfill his lifelong dream of hiking the Inca trail in Peru. There was no way I was going to let him down only 2 weeks in advance (and at his age, you never know if something may happen before we could reschedule...). So following the instructions on the website I wrote to CIC explaining the situation, and they rescheduled it only a month later. The delay was totally worth it to see the look on my dad's face when we hiking