The choice might be easier if we reframe it a bit. How much are you willing to support your in-laws? If they need money, how much are you willing to give them? The entire 50k? More than 50k?
How stable are your finances? What is your emergency fund plan? Have you already worked supporting your in-laws at whatever level you've chosen into your plan?
And finally, what time-horizon are you working with? Are they in good health? Working? Already retired? And do they ask you for money?
I hope these questions are helpful and not obnoxious!
Unfortunately, I don't know of any 'safe' investment that returns better than 1%. And if the time horizon is a few years out yet, you might be better off just rolling it into your overall financial plan, whatever that looks like. Maybe you keep a larger cash cushion in a savings account for helping them, while you invest the other part with an eye to helping out later. If they end up needing any sort of long-term care in the future, 50k doesn't go very far. My friends' father was in hospice for less than a month and it was almost 10k.