Yeah, Dyna Beads work to balance tires.
Once you have decided that you want your tires balanced, I think having them already in your spare tube seems like a good idea. If you went with traditional balancing, you would need to get the tire back on the bike in the exact same position should you need to change a flat on the side of the road. If you had to change the tire, your balancing would be lost entirely, and might even be making things worse with the new tire. With the beads, none of that is an issue.
If you decide you don't need the tires to balanced, then they are a waste of money.