Get a sofa with seat cushions that flip over. That way if the kids ruin one side of a cushion, you can just flip it. It should double the life of your couch!
A fabric that's easy to clean is important. Prints or darker colors are good. Slipcovered sofas are good, you can wash the slipcover. If you want something that lasts long go to a retailer that sells quality and see if you can catch a sale. A sofa is an investment, paying a little extra for quality is a smart idea.
You should be sure to choose furniture that can be cleaned easily, and is of a darker color. This way, you will not have headaches trying to keep it clean. Also, it should be sturdy, quality furniture of a reputable (but not necessarily expensive) brand.
Look for strong stitches. Make sure to get it with a thick stain resistant cloth. Darker colors are always a good idea since they will show stains less. Make sure it has rounded padded edges also.
Look for a hardwood or steel frame base. Lesser quality frame joints will quickly loosen (loose arms, etc). Choose a tightly-woven fabric. The new microfibers are durable and can be wiped down with soap/warm water. Denser foam cusions are also a good choice.
Durability is a key word. Most couches with weak side arms or backs will eventually break with kids. Find a couch that does not have springs in it because those will eventually do go out too. A couch that is easy to clean and low gravity center are good. Keep the couch choice simple and low in cost.