To thicken you can use a cornstarch mixture. About 1 tablespoon of cornstarch to 1/4 cup of liquid, Whisk in until well mixed and simmer or boil a few more minutes until desired thickness. You can use xantham gum as well. It will cause a bit of a gel-like texture if you use too much so start with a little and add more if needed.
A note on the potatoes. When at goal weight they can be used in moderation. There are not that many in here and if you eat 1 or 2 it is not going to cause you a big problem. If your family loves potatoes and are not on plan then use more and just avoid them.
A note on carrots. I love carrots in stews and roast. While they make it go a bit further into a crossover the way I eat them, a few will not be a big deal to you. Just don't over do them. The meal will be more of a S-helper then crossover if you just have a few.