Lily... You're kinda doing it wrong there, that's a final flash ^^u
That is a Kamehameha. The image this drawing is referencing is one of Tadayoshi Yamamuro's Promotional Illustrations, in which Son Gokuu, Son Gohan, and Son Goten are all performing Kamehameha together. In the Illustration, Son Goten's hands are slightly slanted like in the drawing above. It is still a Kamehameha. Just look weird I guess haha