I think it is great to ask when you are in doubt, don't feel like a dork.
Most bloggers that have the blog button html code on their pages put it there for everyone to use! So, I am sure they (as well as I) would be happy to see their button on a blog with a similar theme.
Informing them that you have put their button is, I think, very good. It just shows that you are positive and open for communication. If you don't let them know they will eventually come to realize it, especially if there is any traffic from your blog to theirs and will be glad again :)
http://blog.kanelstrand.com