Drew Barrymore will also star in "Blended"
The film centers on a couple whose disastrous blind date finds them at a family resort with their children from previous marriages. Sandler and Barrymore play the couple, while Joe McHale will play Barrymore's former husband.
Nealon, who was a "Saturday Night Live" regular with Sandler, will play a man staying at the resort with his very attractive younger wife and their son. Crews will play the host of the couple's African vacation who sings and entertains them.
The film begins production later this month, shooting in both South Africa and Atlanta.
Frank Coraci, who previously oversaw Sandler's "Click," will direct the film from a script by Ivan Menchell and Clare Sera. Sandler will produce through his Happy Madison Productions, while Mike Karz will produce under his Gulfstream Pictures banner.
Nealon just wrapped the Steven Brill comedy "Walk of Shame" while Crews, comfortable doing both comedy and action, just appeared in "Scary Movie 5."
Crews has also wrapped a trio of films due out later this year — "Reach Me," "Aztec Warrior" and "Cloudy with a Chance of Meatballs 2," to which he lent his voice.