Yes, there are bikes to rent at the marina at the VWL. You can purchase an unlimited package for you length of stay that includes use of the bikes and the boats for $199. I believe the only thing not included is the use of the surrey bikes, which are for 2-6 people with a child carrier on the front. I am not sure of the hourly price on the bike rentals.
We were there in January and I did see a couple bikes chained to a tree down by the marina, but I do not know who's bikes they were and if it is really "allowed". Even if you have a ground floor room, I do not think there are paths to the patios. You should probably call guest services at the Wilderness Lodge and ask if there are places to leave your own bikes. Please let me know as we have also talked about taking our bikes with, as my parents will be camping in an RV at the campground, and it would be a very easy way to get around!!
There is a very nice paved path that takes you from the Wilderness Lodge to the Campground. It is about a 15 minute walk or maybe about 5 by bike. We walked it many times, and took a surrey bike once.
Have a fun trip!!