Yes, veggies should be steamed. I used this one, and I also have a smaller one now that I'm down to one small dog.
http://www.amazon.com/Oster-5711-Mec...619330-0357661
Carrots are high in sugar, and sweet potatoes are starchy and also higher in sugar. Some dogs will be fine on them, others not. Steamed green beans are always good, as long as there's not a silly allergy.
Hope things are going well.