You could consider using some of the money on a platform like Prosper.com, which is basically crowdsourced personal loans—the loan amounts are in the expected couple grand range, but individual investors only have to contribute a minimum of $25.00 at a time. And there are returns equal to the interest rate the borrower qualifies for (Prosper takes a token amount as the platform). It is decidedly more along the lines of traditional investment as far as building a portfolio with a calculated amount of financial risk, so it'd be easy to view it as a contribution to a 401k or IRA, but on the other hand the people requesting the loans ARE real people, with a need for the money. You see the reason why they're borrowing at the start, whether it's for a large purchase, medical, debt consolidation, etc. The money invested is going to help individuals, not a faceless business, if that puts it in a more pleasant light. It's also pretty hands off and can be automated, so your limited schedule isn't an impact.

(If you're curious, I personally loan on Prosper as one of the ways I invest my savings, but that is the extent of my affiliation, and there are other services like it: Lending Club, SoFi, Funding Circle, Upstart, just look up P2P Lenders and see if any of the big'uns feels like a good fit for you maybe.)