Non-CD options for low-risk investments?

[vanillacourage]

I manage my grandparents' finances. Their preferred method of investment has been CDs - they have approximately $500k invested in about 60 CDs, minimum of $5k each, and have staggered them so that at least one comes due every month.

They liked it b/c it was no-risk and it used to be their thing to drive around to the different banks and shop the interest rates. I have no time for that and have just been letting them renew. The ones coming due this month would renew at 0.9% interest - I'm wondering if there is a higher-performing option with similarly low risk?

As an aside, this many CDs generates a ridiculous level of mail each month and is a total PITA when I do their taxes each year, so that's also motivating me to look at other options.

[keweenawlove]

Our credit union has rewards checking accounts. The interest is 3.25% up to $25,000 and .25% after that.