This is just a thought, but would the people that you are bringing gifts back for, rather that you spend your money on something else? As an adult, I don't care if someone brings me back a present from their trip. (Not that I wouldn't appreciate a gift, but it wasn't my trip, KWIM?)
I agree with the others about the edible MIckey items if you feel like you want to bring something. I don't feel like you HAVE to bring back everyone you know a gift. If I had a friend or family member going on a trip, I wouldn't feel slighted if they didn't bring something for my family.
I hope you have a wonderful trip! (I bet the grandmother's would love a picture of the family at Disney.)
I was going to suggest the picture, but carj beat me to it! Truthfully, that's about all my mom would like from Disney. She's not anti-Disney, but it's not her thing. Also, she's 74 and there's not really anything she needs. I did buy her two of those tiny pocket sized games that they sold at Once Upon a Toy (they probably sell them everywhere, that's just where I happened to find them) because she collected the minature ones. She did enjoy that, but they haven't come out w/ any new ones lately (or least not since my last trip in July of 07) For the baby, maybe a cute Disney bib? It would be cute as well as useful. Not super cheap, but I would think under $10. For school aged kids the goodie bags that another poster suggested is a great idea. Also, if the kids haven't been to WDW, may some Disney one dollar bills. We've given them to kids who have never been and they thought they were so cool. You'd thought we gave 'em a piece of gold.

Also, if you have time to go to Downtown Disney, check out the Mickey mart store (not positive of the name) but everything in the store is $10 or less. They also have some great deals on mix and match items 4/$10. I've bought tons of stuff from there. And my last suggestion would be a Cmas ornament of maybe their favorite character (if they like Disney and have one). Sometimes character ornaments can be hard to find elsewhere. Look for the clearance stickers in the gift shops or ask CM's about sale items. They do have some, but aren't usually to quick to advertise the sale stuff. They'd rather you buy the full priced items.

One last idea, I have... I got a speciality drink at one of our TS's and it came w/ a speciality cup. I asked to have the drink in a reg cup and could I have a brand new clean cup (came w/ a special lid and light up tinkerbell) to go. So I was 'thinking' about giving it as a souvie, but it ended up in my cupboard.

If you don't use it first, I don't see anything wrong it giving it as a souvie. Now, I'd give my DSis one of my used resort mugs, but I wouldn't give it to someone else. Partly because she'd ask me for one of them.
Oh yeah, if they like refrigerator magnets or keychains, they have some pretty cool ones, and antennae toppers (just make sure their vehicle has an antennae, my van doesn't

)
Oh and for the food things... Mickey head rice krispie treats w/ the ears dipped in Choc. The kids go crazy over them.
Best of luck and have a magical trip.
