We were in a similar boat. In-laws lived paycheck to paycheck and didn’t have enough to cover emergencies. My parents were upper middle class and very wise with their money. Once, in-laws totaled their car and needed a new one. We gave them $5K earmarked specifically for the car. Lazy, unemployed SIL found out that DH (her brother) had given their parents a large sum, went whining to them about something or another, and in-laws ended up cashing the cheque and giving the money to SIL, then taking out a high interest loan to replace the car. Lesson learned.
We never give money to poor people anymore. When we want to help, we give tangible help. So, we give them a vacation, not the money to purchase a vacation package. We take them grocery shopping and pay for the groceries; we don’t give them a monthly stipend earmarked for groceries. If you want to be sure that they use the money well and don’t blow it at the casino each month or otherwise use it for stuff that go against your values, it’s much better to give them tangible things that actually benefit them rather than just giving money.
We also don’t give equally to both sets of parents. That depends on the parents’ character though. Will they get offended and hurt if they find out you’re giving to the other set and not to them? My mom doesn’t care. Her investments generate more than enough to live on each year, to the point that she’s actively looking to donate her money to minimize her tax burden. The last thing she wants is more money from us. Instead, she’ll ask me to give interest-free loans to my sisters to purchase a house or let my sister live rent-free in our house. Again, it’s either tangible help or specifically paying for something, not just a monthly cheque. My mom also knows that we help out the other side. She sees it as DH’s duty, so she supports it. But again, that’s her character.
But that really depends on your parents’ character. Some people use money wisely. Some don’t. You know your parents best and know what kind of person they are when it comes to finances. But if you want to make sure they use the money for things that actually improve their QOL, then it’s more certain if you give tangible help or actual things, and not money.