I once went to Mass and as the collection basket is being passed around, I was just calm with my money in my hand. But when the basket was nearing, I grabbed a few miraculous medals from my pocket (I’m a member of the Militia of the Immaculata), and placed them in the basket as I did my money. It was instinctual, and I did not have enough time to think about it. Was it wrong for me to do that?
Sinful? Probably not. A pain in the neck for the money counters? Almost certainly. Not sure what you are hoping to achieve here. Now the money counters have to deal with your miraculous medals, which they will be forced to assume are blessed. It is just going to slow down their process.
I suppose there is a chance the medals might inspire one of them to look into Saint Catherine Labouré, and possibly deepen their spirituality, but frankly, probably not.
On the other hand, one of them may not think about the medals being blessed, not know what they are, and just toss them in the trash. Not a good outcome.
It was instinctual, so I did not have any point in doing except for spreading the miraculous medals. I did not even think about what could happen until after I placed them in, when I thought it would be a pain for the money counters.
Rest easy. Not a sin.