I organised a Charity bike ride from Bangkok to Phuket in 2011, only 850 km in tropical heat and 10 riders. Our longest day was 160km.
Good luck with this and I will share your link on my facebook page. It's a great cause.
We found a blog was good for sharing info in the build up and for the actual ride, the blog site had quite a few visits, we also had a facebook page and a twitter and I built a website that I have now closed. We made T shirts and sold them also, as well as designed cycling shirts for the ride. We also managed to get corporate sponsers whose names went on the shirts/ support vehicles/ website etc
I hope you raise a bundle mate