Well you're assuming those blogs will get traffic and then feed traffic and backlinks through to your main site. Why not cut out that variable and have this extra content on your main site (under the blogs). Surely any backlinks those blogs would attract would then be attracted by your main site instead?
I personally think it's better to concentrate your efforts into building the strength of a single domain (and site) rather than diversifying your content onto external separate domains just for the purpose of getting external backlinks.
I don't think there would be a detriment, I have all my separate sites registered with Google Analytics, webmaster tools etc and I haven't seen any negative impacts over the years.
I'd say if you're going to the trouble of hosting the sites on different IPs that sort of thing to try and disguise the shared ownership from Google, then maybe register them with Google under different names. Really up to you if you think that's worth it, personally I don't.