I have only taken the rickshaw from HRH to IoA, it was me and my young son, and we tipped $5. With BMG personally I would tip $10 or more. I do know that I have seen other threads in the past discussing this question, so you might do an advanced search and see what you find.
The rickshaws are a fun alternative to the boats or walking, but either of those would be fine too. Nothing is too too far from each other.