Can I get in hot water over family members making large ebay purchases with my account?

Tl;Dr – in-laws make high ticket purchases on eBay using my account and they pay me for the purchases. Makes me feel uneasy doing it but unless it’s illegal I can’t easily just say no. Am I getting myself into future trouble?

My in-laws have seasoned, fluid cash that is gotten legally from 1099 contract jobs, and they also have expensive tastes. They frequently find items on ebay that are high ticket amounts and they total way over the CTR limits.

Since they don’t have an ebay account of their own and only a basic credit union account, they are putting the cash in my account (with a national association traditional bank) and I make the purchases on their behalf using my debit card.

We’ve never structured the transactions, but they total easily over $25k over a month or so.

My personal financial picture is very different usually, and this amount is equal to half my yearly salary(!) – very uncharacteristic for my usual deposit activity.

Am I opening myself up for liability? Would FinCEN refer the CTR to the IRS and trigger them to want to tax me on these deposits as earned income? I only want to assist them in purchasing the things they want as they can’t make the transaction on their own, I don’t want to trigger any sort of money laundering investigation.

It makes me feel uncomfortable though, but without any sort of legal framework suggesting this is a breach of my banks terms and conditions or federal law, I find it difficult to say no to their requests. Any money they deposit is a 100% pass-through and I do not earn anything from doing this.

Any constructive advice is appreciated. Thanks.