It doesn't have to be difficult, that's the idea behind the various giving sites that have been set up and why they take their fee.
We just raised £2500 for a couple of cancer charities and all it took was 10 minutes to set the page up and for the members to do their promotional activity to get the money coming in. Once it hits the website it gets forwarded to the various charities based on what splits have been set up bythe organiser.
Setting up a TZ charity or having one member collect the money seems like a lot of hassle for minimal benefit - you can't claim gift aid on money you've collected on behalf of others for example without the donor filling out a consent form with address details etc so you'd be losing 25% of the potential pot straight away (or having the hassle of collecting that data and storing it safely etc too)
/just my 2p