Stock markets already include real estate companies which own real estate directly.
You could buy a fund that already has the allocation decisions made for you, like Vanguard LifeStrategy Growth (VASGX).
That's allocated into:
49% U.S. Total Stock Market
31% Total International Stock
14% U.S. Total Bond Market
06% Total International Bond Market
So that would give both stocks and bonds, along with domestic and international. If the goal isn't a specific amount, then a higher allocation to equities is most likely to have a higher return. If your elderly relative isn't so sure about changes, you might look up the portfolio Warren Buffet plans to leave his wife:
10% short-term bonds
90% S&P 500
Of course, in his case that's billions of dollars, so 10% short-term bonds is enough to live on. But sometimes a relative might prefer to use a name they already know like Warren Buffet, rather than try out something newfangled like Vanguard... at least, I suspect most older people haven't heard of Vanguard (despite it's 40+ year history).