You may also want to think about 'what is in it' for the guest blogger.
Maybe it's just me, but by the time I write something, leave it a while, re-read it, re-write it, leave it, re-read it, fix as many typo as possible etc it can take me a couple of hours to write a blog article.
Always assuming I don't also need to research the topic, get others input too!
So, what's in it for me to post it on your blog, rather than my own (of course this assumes real effort is being made to write a decent blog, not just throw something together) - not saying mine ARE good, but saying I make the effort
Does your blog get read by a large number of people in my niche? Or at least, has one of your blogs in my niche been visited by many people, where I can write a follow up post and you will get the message out that a guest post has followed up one that people read before?
Do you tweet to 100s of followers that you have a new blog post on whatever the subject is?
Have you had any guest posts yet that you can 'name drop'? Don't need to be famous, but show you promote people who guest blog for you.
Do people get a 'profile' for guest blogging? (I don't see a written by element in your blogs - no profile etc.) I know that they may or may not get a backlink if they drop them in the text? But for me, I blog as much for reputation building as for the backlinks (I'll take the backlinks don't get me wrong)
Again, may be selfish, but, especially for a business venture, 'what's in it for me?' is a big thing.
Good luck, hope it all works out for you