My diagram pedal3 in the next post makes these points clearer - but you can get away without the external opamps.
LED displays take a fair bit of current - maybe a LCD?
If you only need 2 digits, how about a small 2-digit seven segment display?Sparkfun carries this little 4-digit bubble display, I use 2 of them on this 8-digit display board
1/ You don't really need opamps - it just takes the guesswork out of finding r3,4 values.2/ A LM358 won't quite do - you need a rail-rail opamp.3/ If you intend to use high current displays, opamps would be a good idea - but be sure they've got enough drive capability. LED display - the worst case is displaying '88', with 14 segments on. Allowing 5mA each that's 90mA - more than most opamps can handle..But, of course, you could drive them directly from the supply with suitable drivers..... I'll have a ponder...Allan.
Just saw your post , crossroads - neat little displays. But this is next next to his pedal - 4-6 feet away? so perhaps too small - and of course the reading angle is limited.
Here are 4 different sizes of 2-digit displays, 0.3, 0.4, 0.56, 0.8 inch:http://www.kingbrightusa.com/category.asp?catalog_name=LED&category_name=KC2%2DDigit+7%2DSegment+Thru%2DHole+Display&Page=1
Add MAX7219 to make it SPI.It's available SMD & thruhole, I don't about SMD except from Digikey/Mouserhttps://www.digikey.com/products/en/integrated-circuits-ics/pmic-display-drivers/729?k=max7219