That would depend on how old they are now. Ages in the guidelines vary a little, but usually go something like this:
starting at hatch, 1/2 square foot per chick
at 2 weeks, increase to 1 square foot per chick
at 4 weeks, increase to 2 square feet per chick
at 8 weeks, increase to 4 square feet per chick or adult chicken
That does not mean you need to exactly double their space on that exact day, but it does give a fairly good idea of how much space is appropriate at what age.
The basic idea is that they grow VERY FAST and they also become very active, so they need adult amounts of space within about 2 months of when they hatch.
Yes, they can sometimes be crowded a little bit more than that, but more space usually means less problems. This applies to behavioral problems, health problems, and cleaning/smell problems.
"Too much" space does not ever seem to be a problem. (Possible exception: for about the first 3 days, they might wander away from the heat and get lost & chilled, so spaces bigger than about 6 feet across might need special management during those first days. But after that they tend to do fine even with enormous amounts of space.)
I think a lot of people see tiny little chicks and underestimate the amount of space they will need as they grow up. Also, a small space can be fine for a short time (like a box as you bring them home), but it not fine for longer stretches of time (several days or more.)
The guidelines I find say 3 to 4 square feet each, so about the same as a chicken. Since you have mostly chickens and only a few guineas, I would plan on 4 square feet each, which keeps the math simple.
If these are your first guineas, and you only have 3 of them, I would probably leave them unclipped. That way you can learn what is normal for unclipped guineas. If you get more guineas later, you could experiment with clipping some, and then you would be able to see if it changes anything. Or you could clip one of the current 3, and keep re-clipping it as it grows, and see whether that one behaves differently as an adult. (Although with only 3 total, the personalities of the individual guineas might make more difference than the wing clipping, so you may not be able to tell for sure.)
