I am an avid reader so this is something I tend to do even if there is wifi, but it is one of the best things to do without an Internet connection. If books aren't your thing flipping through magazines is the next best thing, I have a huge pile of magazines I keep just in case (great for road trips too).
There are many book apps you can use as well that don't need wifi (as long as the book is downloaded onto the app). There is a library app called Overdrive where you can borrow audio and digital books from your local library with your library card account, that is great. There is a social book app call Wattpad where people can write books and and anyone can read them, most of them are fan fiction ,but you can find some great books on there. The other common apps are iBooks and Kindle where there are only a few free books, but you can definitely buy a book as well.
If you have a lot of people who want the wifi back why not pull out the old board games and play a game. Everyone loves group games every once in a while. If you want alone time though, there are a few games in the App Store that can keep you busy.
There are a lot of things you can do, but I hope you enjoyed these four tips on what to do.
Let me know what you do without wifi.