Working!!, Shinryaku! Ika Musume Recommendations
Both settings are in a Restaurant.
Both have characters (Aizawa Chizuru of Shinryaku! Ika Musume, Sato Jun and Kyouko Shirafuji of working) which the main character (Ika and Souta) won't dare mess with.
Both were safe enough to be viewed by elementary school kids.
Both do have either a shallow or unstable plot.
Both characters (Souta and Ika) never intended to work in the restaurant in the first place.
And both have little bit lesbian that goes in it.
One was set in the suburbs of Hokkaido while the other one was set on a beach somewhere in the southern part of Japan (In Okinawa... I think).
Both are slice-of-life/comedy series set in a restaurant.
Apart from the similar settings, the characters and the humor are also somewhat similar (notably, Chizuru and Yachiyo, Ika Musume and Yamada, running gags involving damaging property, questionable obsessions).
Working!! is a bit more mature overall, although both are highly accessible and enjoyable.
Both are great shows; slice-of-life, comedy, gag genre.
What's most similar between the two is the restaurent setting and the comical feeling it gives!
Both animes surround the lives of the people working in the restaurent...though Shinryaku! Ika Musume is more focused on the antiques of the protagonist while Working!! depicts the relationships among the co-workers...
And ofcourse both are hilarious shows and great to pass time :D
They involve a direction in working at an established food business and focus mainly on the workers with comedic interactions from returning side characters. Even though they have differences in stories, Squid Girl and Working have a lot of similar slice of life scenarios outside of their restaurant focuses.