It’ll be an awesome experience, one you’ll probably never forget, don’t let the fundraising put you off.
Split it down in to smaller chunks for starters, spread it over the time you have to raise it perhaps.
If you’ve got any contacts through work approach them,I riased over £9,000 for a John O’Grats to Lands End ride last year and got a lot this way, even in the current climate.
I know one ride that had different shirts made up for each day that were sponsored by different companies.
Also know of someone who rasied over £2,000 from a raffle, got the prizes by writing to hundreds of companies and was amazed at how much free stuff he got!
If its for a specific charity, use them, I got them to set up a bucket collection at a cardiff city football match for me (did it with a load of friends) rasied around £1,500 in about an hour and a half.
Good luck!