It seems unreliable that you rashly invited two old people to go to the jewelry store to buy rings with you young couple.
I feel that the old man will not take away the extra money. More than 10 thousand is even more impossible; Usually, if you have anything to do, you should take out your money for later use. Go to the jewelry store and choose a ring without saying hello. Where did the old man get this cash? Even if the old people will pay by WeChat or Alipay, what will your girlfriend think of you if you don't make it clear in advance and let the old people pay temporarily? In the future, your lover will say:
"I got married once in my life, and the wedding ring was bought by the old couple. You're watching. The old couple paid for it. " Is this possible?
Imagine: one day, when your money is ready, take your girlfriend to a jewelry store and let her choose a ring freely. You will enjoy this warm and elegant scene, pay happily, and then leave the jewelry store gracefully and slowly with your beautiful girlfriend. What a romantic scene!
It doesn't seem appropriate to deal with this matter according to your current economic foundation.
Since you are not rich for the time being, you can not buy a ring for the time being. The plot of engagement and proposal can be postponed. When your financial situation improves and allows, it is not too late to deal with the situation of "proposing marriage"
You also said, "... they are old and in poor health. "This kind of thing should be solved by yourself.
The money in the hands of the old couple had better be reserved for their own use when they are old.