if you're just looking for snack-like non-perishables for only 2 people, putting those foods in a carry-on is definitely the way to go.
If you're looking for things that need refrigeration, I can suggest Gooding's to you (
www.goodings.com). The thing I liked best about their delivery service is that you don't need to schedule your delivery time and you don't need to wait around your room and be there for the delivery (instead of getting out and having a fun beginning to your vacation). Gooding's delivers to Bell Services, then it's up to Bell Services to deliver it to you. If you're not in, they hold onto the groceries for you and even keep the cold stuff cold; they leave a message for you and they wait until you call to tell them you're in and you'd like your groceries now, please.
I don't often get rental cars when I travel for leisure, unless the vacation itself entails traveling from one place to another. But when I have gotten rentals, I would have LOVED to have a place like Gooding's to deliver groceries to me, rather than having to take time away from the start of my vacation traipsing around a strange supermarket and waiting in line, then checking into the hotel with not only my luggage but other packages as well. The thing that sold me on Gooding's is the not-having-to-wait-around-for-the-delivery-in-your-room thing. Other people on this board swear by stand-alone delivery services (they are not a store -- they shop wherever you want them to) such as
www.wegoshop.com and
www.gardengrocer.com, but I haven't heard that they have the same convenient delivery policy as Gooding's does. If they do have that same method, that you don't need to be present for or wait around for your delivery, then I think I might prefer them because, from what I've heard, Gooding's is the most expensive supermarket in the area. You can have the stand-alone delivery services go to a cheaper market.
You have lots of options. Good luck, and have fun!