Are you wanting a bag for airline travel? I'm also wondering about the comment of maybe wanting a bag with wheels. If you want a bag for airline travel, I think many SM travelers, especially those in the show ring who fly with more then one fluff, recommend these.
Pet Carrier
Personally, any carrier I've seen with wheels has an awfully small compartment and no suspension at all so your babies would feel every bump. I don't know about yours, but mine would be terrified. Pat's suggestion of a stroller is the what I would recommend too. In fact, when I do plan on flying with mine, I plan on using the Sturdi Carrier that others swear by, but have a stroller as well. That way I can stroll them, the carrier, my purse and carry on all in the stroller up to the boarding gate, then let them put the stroller on the plane. I hope they would do the same for a fold up pet stroller as they do for baby strollers. I'll have to check that out for sure before I do fly somewhere.