You could try this
family presents.xlsm

It takes the 6 families and assumes 2 presents per family distributed to the 12 kids (ie 1 present per kid) and excludes the kids in their own family.

You can put up to 3 kids into a family (left side of spreadsheet - yellow area - which will ensure they are excluded from their own family giving) and press the run button to generate the distribution. It only really random generates the top line then allocates based on the remaining availability.