My suggestion is that you move to a platform that is extensible. I'm a Joomla developer, so of course that is my preference, but there is good reason for that. With Joomla, you can have your blog, you can have your ecommerce, and if you want an online, there's an excellent component for that that can be added later and it integrates with everything else on your Joomla site.
WordPress is the fabulous for blogging and more. If you want primarily a blog plus some other things, that's perfect. If you want a website that also has a blog, I would suggest Joomla.
There's a WordPress integration available for Joomla if you want to keep WordPress.
Ning is a hosted solution, so you don't have as much control over it as you do your own site on your own webserver.
Joomla and its third-party components are all open-source so you can have your programmer modify it to suit your needs if necessary.