Entering double interval (unbroken) grace notes?

I suppose you could say that. The two would be played simultaneously but just as quickly resolving to a primary two note chord just as any grace note instantly slides to a primary note. As an example, a Gb and Bb played simultaneously then, in grace note fashion, instantly sliding to G & B natural. You hear this commonly in country piano styling.

Thanks for Handbook reference! I wasn't aware that the key would stack two grace notes together as a chord. So good to have you guys around.