What is risk tolerance of the parent? This is the most important thing to understand.
Least risky is t-bill, Ibond, whole life insurance, single premium fixed annuity (my father is in 100% SPIA because zero risk tolerance). Then there are bond funds of varying "durations" (longer is higher yield but riskier), municipals, foreign bonds, convertibles, and even Preferred shares. Do you need want a "cash" or equivalent bucket such as money market, CD ladder? Is the reason for such a high Fixed percentage the intent for a 'zero capital gains' portfolio? That bears consideration of Dividend centric etf's and maybe a larger allocation to REIT.
Universal advice as you explore this...do NOT ever 'chase yield'. This is just as true in fixed income as it is in equity. High yield stuff is shiny and kind of sexy but it is the market signaling it smells high risk. The market is usually right on that point.
NOTE: 70% is about the max for fixed income if you believe in the CAPM and EMH. Above 72%, you are actually become more risky instead of less with higher fixed allocation as your portfolio is becoming so highly correlated. Math and stuff...