Combine the almonds and walnuts in the bowl of a food processor and pulse 5 to 6 times to coarsely chop. Add the dates and process until the mixture is very finely chopped. Add the juice and process just to combine; transfer the mixture to a small plate.

Make sure the grapes are dry. Scoop up a heaping tablespoon of the date mixture and pack it around a grape, completely covering to seal. The mixture will become slightly sticky and oily as you work with it. Repeat with remaining grapes and date mixture.

Roll the balls in seeds to coat. Store in a covered container in the refrigerator for up to 3 days.