I think it's hard to take your bicycles onto the bamboo rafts, but you may consult this with the owner.

you can put 2 bicycles on one bamboo raft. Did that last week from Yulong bridge. the ride does not pass the big banyan tree but it can go to gong nong bridge if you want. That would take 4 over hours. Contrary to what the above article says, it takes more than 2 hours to reach yulong bridge by cycling on the country roads on the shores of the yulong river.