First, I would not want the air pulled in through the cracks and crevases. Second, If your house has obvious cracks like that, its time to get out the caulking.
Third, the make-up air could be fed into your return air system on the furnace. Then it would be "conditioned" before comming into the house. A fan strong enough to change the air in the basement 6-10 times a day can have the make-up managed or it can be guessed at. If your basement is only 24' X 40' you are moving 76,800 cubic feet of air from somewhere.
Glenn