Hey there, Cosmic Atheists, welcome to the forums.
The great trick that Creationists pull with regards to vestigial organs is to claim that "vestigial" means "useless". It does not. It means that the organs have lost their original function. The other 'uses' in vestigial organs can usually be seen in the ancestral organs as well.
For example, yes, we use our tailbone to walk and digest. So do most other mammals. That doesn't wipe out the fact that this tailbone begins post-anally in the embryo (like all other tails), and that the vertebrae type are the same as seen in other closely-related mammals.
Whale pelvises and leg bones are a good example as well. Yes, whale's reproductive muscles are anchored to the pelvis bones (just like all four-limbed creatures), but that doesn't address the clear evidence that they are vestigial, mainly by the clear progression we see: some whales are born without leg bones or pelvises (clearly disproving the creationist idea that whales need their pelvises for reproduction)... some species have only the pelvis, some have both pelvis and leg bones, and finally in the fossil record we have whales with pelvises, leg bones, and little feet (five-toed, no less! Why should they be five-toed feet, if they have no relation to land animals?)