These are two different quests.
I don't recall what they are called.
In the one with the little boy, actually there were two children when I played it. Go to the house and become friends with one of the adults, it does not matter which. Once inside, go to the little outbuilding, ignore the children if they follow you, they aren't interested in what you are doing, examine the hole in the wall thing to gain access and you are on your way - whatch out for traps etc.
In the other one it's quite a small house, you have the name of the owner, so it is easily found in town view. Make friends with the owner to get inside. There are number codes found by 1) Flush the toilet. 2) Turn on the stereo. 3) Read a book. Make a note of each code in the order given above. Use the stairs into the basement and then work out how the first set of fgures will open the doors to the next level and so on.