You have one P-38 made in 1941 by Walther marked AC 41. The other P-38 was made by Mauser in 1944 marked BYF 44. The Walther PPK is a real nice one but without seeing the serial number I cannot date it. One Luger being an S42 was made in 1936 by Mauser before the Nazi requirements went into effect in 1939 if I remember right. It was what have been called a sneak gun to stay within the requirements of the WW1 treaty. The other Luger also made by Mauser and made in 1941 marked BYF 41 stamped. All of these firearms are in excellent condition and are well taken care of. Your dad has done a great job of that. They are worth quite a bit of money just because of their condition.
Value wise the P-38's I would say a value for insurance would be $1500 each. The Lugers because of condition I would say minimum of $2000 each and the PPk if it's WW2 at $1500 with the case minimum.