You will get lots of support on this forum and many people go back to very tiring, physically demanding jobs... I am hoping you will get lots of great advice this evening.
I completely understand where you are coming from with your income and children's ages - and the responsibilities you have are huge with young children.
I was forty when I had my hip replacement, with two children (same age more or less) and obviously I am quite fit and healthy - I love the gym and still do....but, and I have to be honest I am not sure I could ever go back to a proper physical job like flooring.
My surgery was very successful, and I go to the gym, play sports, but all of these things can be stopped when I am tired or it is starts aching, they also do not require getting up and down from the floor all of the time.
In fact even at my young age I tend to find getting up and down from the floor quite tricky even now - it is probably the hardest of all the things we do (I am 18 months down the line) I have mastered doing it more easily now, but I wouldn't say I was leaping up and I don't think I could do it all day. I don't want to worry you I really don't, as I know you are in a really difficult position but I think your doctor might be right, and certainly even if you can go back to flooring it wouldn't be for a long time after your surgery.
I really hope you don't think I am being negative, but there are some jobs that are going to be harder than others post surgery and this is probably one of them. That said with lots of breaks, rest, and care you might manage it...some people do the most amazing things we have seen people achieve the impossible on this forum so many times.
I can bend 90 degrees no problem - but I am not sure about all day every day for another twenty years to your retirement.
Is there any other position in your company that you could consider doing? If you are not in complete agony have you time to retrain for a new job that would be easier for you? This is a lot to take in, and especially you have only just been told you need a THR It is a horrible shock.
I am hoping many of us will post on here with their experiences and can help you with solutions.
This forum is a great place for advice and information - so welcome and wishing you well.