Ne-Yo Can't Stop Smiling on Family Trip to Disney's California Adventure

Ne-Yo's face is probably hurting this morning ... all that smiling has surely taken its toll.

The singer took his fam bam to Disney's California Adventure on Tuesday ... and the bunch couldn't look happier. Ne-Yo was all smiles as he and the kiddos -- Mason Evan and Madilyn Grace -- hit up Mater's Junkyard Jamboree (trust us, not just a kid's ride).

His wife, Crystal Smith, also looked like she was having a ball ... and, btw, looking very pregnant.