Don´t export the file for the internet directly from After Effects. In case the bitrate is wrong you need to do all the rendering again, harddisk space is cheap, so don´t be afraid of a 4 GB file.
You do not need to export a lossless file (uncompressed), though. Mild compression is easy and saves you a lot of space. On Mac the choice would be ProRes, on a Pc the free AVID DNxHD codec. 16bit is right, no need to go higher. Color working space set to none is fine as well when working with the DNGs.
Once you rendered your file (Quicktime ProRes 220 on a mac or QUicktime DNxHD 185 - only this one supports 16bit), make sure you set the output to trillions of colors) you can load it in Adobe Media Encoder to transcode it to a internet friendly format. Start off with a H-264 file that fits your size best. Often you do not need to provide a real 1080p file, most VIMEO videos in HD play only in 720p. Then play around with the bitrate. Do you want more? Incrase the bitrate.
Two pass encoding and the checkbos "Maximum render quality on" on the lower part of the AME window should give you best results.
If you want to know more about rendering DNG sequences in After Effects, check out this article (just skip the LOG functions entirely):
http://hackermovies.com/hackermovies-magic-lantern-raw-workflow-guideHappy encoding!
Steffen