We Beed to look after selves as well as our family and children. We need good deeds for our future as much as we can. We also should for our family and children Whatever they need to have a respectable livelihood till they are able to earn for themselves. Obviously, we believe that Allah (SWT) will never leave them as He never left us.
Yes it is allowed for every Muslim to invest his money after being sure that money will not be invested in unlawful business i.e. alcohol, interest, etc.
Khums will be applicable on the investment on the date of Khums.