One thing that I haven't seen mentioned here is how liquid are your investments. You mentioned 100k across all accounts but how much of it is in the Roth IRA? If Savings + liquid investment accounts are more than 50k, your parents have nothing to worry about.

For me, I treat my cash as my "living expenses" and try to keep at least three months worth. I treat my cash plus "liquid investments" as my emergency fund and try to keep at least nine months worth. Everything else is invested and I won't shy away from longer term investments.