We want to weigh up to 3 people. So the measurment dusn't have to be real precisely.
We measure with steps of 60kg.
My native language is dutch, but reading englisch isn't hard for me.
Writing englisch is still a litle dificult for me. So this is a good exercise for me as well.
Will they be standing on each others shoulders? Hanging from a rope? All sitting on the same chair? Standing on a platform you will build -- With force sensors (strain gauges) at the corners?
"doesn't have to be real precise" Steps of 60Kg? Why bother? It seems useless. That is plus or minus the weight of a teenage student is it not?
Now do you mean the display is in steps of 60Kg -- or the sensors? I am not aware of how to build any weight measurement device with that level of inaccuracy. Maybe +- 6KG-10kg???? Base on say three people of 60-80 kg each then... say 240KG +- 5% would be about right for a simple "dumbed down" project.
Always separate the "working part" from the display. Just like object oriented programming.
Why build something of say 30-50% accuracy. Use a weight guesser at a local carnival... it would be more fun and just as instructive.
Now if this is a project for kids under 13 OK -- but if this is a "High School" (Grade 10-12) project maybe you should define it a bit better.