The network announced Monday that Grande, 26, and Lovato, 27, will perform remotely during the TV special, which airs Thursday at 8 p.m. ET.
Josh Groban, Elle Fanning, Darren Criss, Alan Menken, Tori Kelly and Marcus Scribner have also joined the lineup. In addition, the event will feature Kenny Ortega and the High School Musical and The Descendants casts performing "We're All in This Together."
Grande will perform the Hercules song "I Won't Say I'm in Love," while Lovato will perform "A Dream is a Wish Your Heart Makes" with Michael Bublé. Criss will perform "I Wanna Be Like You" from the Jungle Book, with Kelly to reprise her cover of "Colors of the Wind" from Pocahontas.
Previously announced guests include Christina Aguilera, Erin Andrews, Bobby Bones, Kristin Chenoweth, Auli'i Cravalho, Luke Evans, Jordan Fisher, Josh Gad, Derek Hough, Julianne Hough, Carrie Ann Inaba, Little Big Town, Kenny Ortega, Donny Osmond, Thomas Rhett, Amber Riley and John Stamos.
Disney Family Singalong is meant to uplift and entertain people amid the coronavirus pandemic. The special will also feature PSAs to raise awareness about Feeding America and its work to help people struggling and facing hunger for the first time due to COVID-19.
"If there's something that we've all learned in the past few weeks, it's to cherish every moment and the importance of connection, whether through laughter, stories or music. We hope that we can help create some new unforgettable moments in everyone's home in a way that only the magic of Disney can," ABC Entertainment president Karey Burke previously said.