This is only their second summer, but already those distinctive yellow rickshaws of Vineyard Pedicab have become a staple of downtown Oak Bluffs.

During the recent heat wave, while most people were at the beach or in air-conditioned rooms, the young men and women of the pedicab company could be found pedaling passengers all around town. They perform a valuable service, getting people to their destinations while giving them informal tours of the downtown, always doing it with a smile.

And they do it all for a pay-what-you-can price, working only for tips.

But toned calves and polite demeanor tell only half the story. All the money earned by the company through the advertisements placed on the pedicabs goes directly to the Pan-Mass Challenge, the annual bike-a-thon which raises money for the Jimmy Fund at the Dana Farber Cancer Institute.

On top of that the company has launched its own bike-a-thon to raise money for cancer research on the Vineyard; the second annual Pan-Martha Challenge takes place this weekend, starting with a benefit party at Flatbread at Nectar’s in Edgartown tonight at 6:30 p.m.

Registration for the 50-mile ride is tomorrow morning at 8 a.m. at Ocean Park in Oak Bluffs, and riders set off at 9 a.m. The course spans the Island, ending at Ocean Park and a post-ride party at Park Corner Bistro.

Jenn Warden, one of the pedicab riders and organizers of the Pan-Martha Challenge, said 15 riders participated in the event last year, raising about $7,000 for the Jimmy Fund at the Dana Farber Cancer Institute. Organizers this year hope to increase the number to $15,000.

Ms. Warden said there is a nominal registration fee of $25 and a minimum pledge of only $100, much lower than the Pan-Mass Challenge which has a minimum pledge ranging between $500 for the shorter routes and $4,200 for longer ones.

She also said this is a ride for everyone.

“We want riders of all skill levels, from the hard-core biker to the beginner. We’re not blocking off roads, we’re not stopping traffic, and people are encouraged to go at their own pace. Last year we had people finish the course in one hour and 45 minutes, and others finished in four hours,” she said.

Ms. Warden said the idea for the ride came from Kevin Murphy, the founder of Vineyard Pedicab. Mr. Murphy first established the pedicab company in Newburyport in 2007 after he lost both his parents to cancer, and has since donated every dollar he has earned to the Pan-Mass Challenge.

Mr. Murphy runs the company with his friends, John and Will Pasquina. From the start the three have emphasized charitable giving ahead of profit. “I think everyone can relate to what we are trying to do, because everyone knows somebody affected by cancer,” Ms. Warden said.

“Last summer my mom had breast cancer, and we have riders with relatives and friends who have been taken by cancer. It means something to them. As we’ve gone around the Island looking for support [for the bike-a-thon], we haven’t really had to sell this whole idea, because people are into it. They want to support the cause,” she said.

Mr. Murphy said many people hop in the pedicab not knowing about the charitable component of the company.

“They just want a ride up the street. Then the riders tell them about what we do, or they read the mission statement in the cart, and their whole experience changes. Once you start the conversation about cancer you find everyone can relate, almost everyone has lost someone in their life to cancer,” he said.

Mr. Murphy is hoping to double or triple the amount raised in the Pan- Martha Challenge last year, but agreed this is still meant to be a low-key affair. “Maybe some day this will become something bigger. But right now it’s a chance for someone who can’t raise the $4,000 for the Pan-Mass Challenge to participate and do their part,” he said, adding: “We keep it simple. If you can ride a bike, you can help.”

The Pan-Martha Challenge begins tonight with a benefit party at Nectars/Flatbread at 6:30 p.m. featuring the MV Afro Beat Project with Tom Major of Entrain, Yvan Agboo, Alex Bundey and other guests. Registration is Saturday morning at 8 a.m. at Ocean Park in Oak Bluffs; the ride starts at 9 a.m. There will be a post-ride party at Park Corner Bistro. All levels of riders are welcome.