Maybe your father in laws silence or apparent disaproval of your answer is because of his one fear -he wants your mum to be absolutely fine because all of us will face this at some time,he doesnt want to face reality, so he wants a different answer even if it isnt the truth.
Emz is right i dont think life ever does go back to "normal" how can it when the person we lost was such a large part of that "normal" But be wary also of what we consider normal is -because society and even some forms of psych theory sees normal as "cured" the theory is you follow a linear pattern of grief, and indeed some of those stages are recognisable - shock guilt anger etc and you follow it then break the bond that ties you, then youre "cured" i think the official word is detachment - it seems to me such twaddle like the year of mourning thing - grief doesnt have a sell by date. - but we go along with it because we,re expected too we say we,re ok when we are not, we go back to our life as it was before, pretend to be the life and soul of the party if thats what we were before - because that was "normal," maybe we even believe ourselves "cured" - until something knocks us sideways and we,re in a heap crying again.
There is another theory though called continuing bonds and to me this is more realistic.Our culture, history belief system will dictate too a degree which direction this takes, it could be religion, heaven, reincarnation,etc so we think of them as looking down from heaven,we see them in an animal we suddenly see regually or a new borm baby in the familly,we take part in a ritual.of some kind, perhaps we lose faith and explore other ideas . Even if we believe in none of those things it doesnt prevent us from doing this,we seek closure but how can there be closure and actually do we really want that -maybe we think we do, so we can go back to being ourselves -but being ourself without the people who shaped us isnt being ourself either.
So i think the key is to do those things, live our life and have those adventures,but stop thinking in terms of trying to do that without them, which is what makes them empty -and find a way to take them with us.It could be simply taking something of theirs everywhere with us, writing about our advetures in diary form adressed too them, think about them in our decision making as though we were talking too them, what would they say what would they advise, maybe make some of those adventures all about them,go somewhere or do something they wanted to do, continue an interest they had so that in a way we may actually come to understand them better and carry their legacy forward that way. Also dont be afraid to go back somewhere because its going to evoke memorys and make us sad, go back because, even though that happens, it also focuses on the happy memories.
We used to go somewhere we both loved for holidays whenever we could get away, and although in the first year i thought it would be too painful so didnt go, and i,m now restricted to once a year, i feel closer too him there than anywhere, i had to slay some dragons on the way to going back, but i,m glad i did now.