PWM Allocation Strategy for Older Retirees Historically all Money Mkt

Question to some of the more senior PWM people on the site. I just learned that my retired parents (70s) have basically all of their savings (retirement accounts + investable accounts) in CD/money market accounts. I'm trying to convince them to pivot so a better mix. For context, they don't even need this money as their social security + pension inflows are greater than their outflows. Lets say I could get them to invest it and/or hire a PWM type person. My question is, given the recent run up in the markets (of course could go higher, or lower) it seems difficult to just instantly reallocate. So lets say you were to get a new account like this, what is the best strategy to start shifting the allocation mix?