The whole family consists of 4 + 2 + 1 = <<4+2+1=7>>7 persons.
The entrance ticket to the park costs the same for every person, so the family would need to pay 7 * 5 = $<<7*5=35>>35 to enter.
For visiting the attraction the tickets would cost 4 * 2 = $<<4*2=8>>8 for the kids.
Their parents and grandmother would need to pay 3 * 4 = $<<3*4=12>>12.
That means a total cost for the family standing at 35 + 8 + 12 = $<<35+8+12=55>>55.
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