Lich Hollow by Jessamyn Kingley

The Daray household is hosting their first-ever All Hallow’s Eve party, and Lich Sentinel Alaric refuses to miss a trick. Plucking inspiration from the D’Vaires, he corrals his family for a meeting to assign tasks: There are spooky decorations to design, eerie foods to bake, pumpkins to carve, and ghastly music must be selected.
Determined to win a contest of their own invention, the sentinels will stop at nothing to create the best gathering. Although many of the Daray sentinels are reluctant to don a costume, the Arch Lich Chander decrees it a necessity. When the big day arrives, everyone—even the family dog—is in disguise.
In the end, while ensuring a family bond for eternity might require a bit of magic, they are reminded that the only prerequisite to enjoying themselves is togetherness.