Need advice on best route to take

Hello,
I’m a web designer and I’m just getting started with www.remarpro.com sites. I do not know html and css the way some developers do but I know enough to have laid out several sites using html and css. I’ve reskinned a wordpress.com site for a yoga studio but now I think they may need their own custom www.remarpro.com site so they can take advantage of some widgets etc. I’ve also just designed a site for a nutritionist and she decided she wants to have a blog. I haven’t actually installed wordpress yet because there is something I need to know before I do so. When I selected wordpress 3.2.1 as my version, I just had to pick something. I’m using Dreamhost as my host, I’m not sure what version they use in their one-click install. Anyway, blog is going to be one of the links in the main navigation. What I want to know is, would it be better to install wordpress into it’s own blog folder and keep the advantages of wordpress tied to just the blog or would it be better to make the whole site powered by word press and take advantage of it’s CMS capabilities and some of the widgetss on non-post pages. The possible cons may be that when we try to use some of the software she wants to include in the site such as schedulicity and squareup,I don’t know if they’ll work well on a wordpress site. I also am wondering if this will make things harder for me since I’m just learning this. On the other hand, it would be nice to have a CMS for the entire site and to be able to have a twitter widget on the home page but if it’s a pain to implement, it’s not that important to have the CMS. I still have to read about wordpress template files etc. I will have two main page designs, one for the homepage and one for the other pages. So far I have the non-home page design built out in html, css and php includes. Just one of the pages is up so far here: https://mindfulnutritioncoaching.com/about.php I haven’t done more because I figure I may need to convert this to a wordpress template. Any advice to help me decide if I should use wordpress for just the blog portion of the site or do more than that?