This has two advantages; first the tax advantage of keeping more of the money in your family (since any large pot of money left when you and your partner die will be taxed at a very high estate tax rate, in excess of 50% before it can be given to inheritors) without having chunks of the gifts bitten away by taxes. If, say, you were to personally give a relative $100,000 they would have to pay income tax on the money above $11k. From a tax standpoint you are much better off giving yearly gifts of around $22,000 (which will probably go up with inflation).

Also, you cite concerns about favoritism; if you were to give all of the members of your family the same gift (explaining the tax advantages) and then simply keep giving the gift to certain preferred members, this would probably cause less familial strife and envy than giving huge lump sums to favored relatives.