Check out Series I government bonds, a savings bond that earns interest based on combining a fixed rate and an inflation rate. https://www.treasurydirect.gov/indiv/research/indepth/ibonds/res_ibonds.htm I just noticed that this has a $10,000 maximum, so this will not help him.
If bonds (muni or corporate) are deemed the preferred path, it may be worthwhile to request guidance (a ladder plan and initial recommendation - as mentioned by zghorner) from more than one broker! You may be amazed how beneficial this can be (to find broker who understands and wants your business). I requested same from 2 brokers many years ago, and was easy to determine which really had knowledge VS who just wanted your money (without effort).
Pops might want to drop some fun money into bitcoin on a regular ongoing basis via dollar cost averaging using something like Swan Bitcoin. https://www.elitetrader.com/et/thre...-and-business-poll.335193/page-4#post-5363862