An iso file is just a mirror image of your DVD. Since iPads don't play DVDs, they don't play iso files either. And apps like Air Video wouldn't stream them either, since iso files aren't video files. I don't know how it works on a Mac, but on a PC you can mount iso files as a virtual DVD drive and assign them drive letters. If you can do this on a Mac, then you could point Air Video to the virtual drive and it might stream from the virtual drive. But you'd have to mount your iso file first.
On the other hand, I don't know what you did to create your iso files, but if they are exact copies of the original DVDs, then transcoding them to iTunes format video should give you the same quality videos as you would have gotten if you had transcoded them from the original DVDs.
the whole idea is that i don't want to spend time to transcode...i have thousands of iso files...
On Mac, i only need to click on an ISO file, it plays natively.. with "DVD Player"