There are two kinds of 1/4" cables used on small mixers - balanced and unbalanced. XLR IO is balanced. Balanced inputs and outputs have better noise rejection, particularly over long distances. A balanced 1/4" jack and a balanced XLR jack are almost interchangeable. There is one functional difference (beside the obvious physical one)
The primary difference is what happens when plugging or unplugging the cable. With an XLR cable, all pins are individually connected, and there is no shorting of pins as a result. With a 1/4" plug, there is a brief moment where the contacts of the jack sweep across the inserted plug and cause a momentary short. This is the "thump" you hear when pulling cables or pushing them in. You can, of course, avoid this by cabling the jacks before powering them on, etc.
Small mixers typically use 1/4" outs to save space and possibly cost. But usually space. If the 1/4" outputs of your mixer are balanced, your adapters will work fine. (The dirty secret is that for 20', they'll work fine anyway even if it is unbalanced).
The consideration for gigging is those adapters are now critical to your rig. You forget one, one goes bad.... no sound. I'd add them to your spares kit. But a pair of cables to serve as your 'mains" wouldn't cost a whole lot either and you could have them terminated however you needed - 1/4" one end, XLR the other, or whatever you need.
In the end, you'll just have to decide what seems best, spend a little more on a mixer, spend less on mixer, more on cable, or less on mixer and use adapters.