Hi Stephanie!
Quick service meals are usually cheaper than purchasing the dining plan. However, since you have some table service options in mind, you may want to consider using the dining plan if it will save you money.
The way I like to find out what is more economical is to map out, in general, where I'd like to eat along with how much it would cost. You can find most of this information on allears.net - the dining section lists menus along with the prices of the meals. (As always, prices are subject to change.)
Once you've completed this comparison, it should be more clear on what the better option is. You also mentioned you will be traveling in August. If your dates are August 16th or later, you may want to take advantage of the
free dining offer Disney currently has available.
Have a fabulous vacation! Diane