How do I keep my 5 year old occupied?

I have a 5 year old stepson that will be with us the whole summer. He's usually with us one weekend a month, so I'm kinda nervous about this. Mainly because he can't stay focused on one thing longer than 10 to 15 minutes. And he always wants me to watch him and do everything with him. Which normally I don't mind, but I think it will drive me crazy if I have to do it for 3 months (I will be home with him all day). We live in the country, which he is not used to, and only has one friend here. Any tips?