My husband once found a huge clutch of guinea eggs in our cherry orchard.
We did not know how fresh they were. We have a 60 egg incubator and set all the eggs that were not cracked or damaged or had poop on them.
4 weeks later, just as i was thinking they were all bad as i did not hear any peeping or see any pipping and was about to throw them out. I went to the bacement to check, and ALL but one had hatched overnite!
So in one day we went from 6 guineas to over 60!
The float test is great for figuring out the freshness of eggs for eating.
I do not think you should be doing the float test on eggs you intend to hatch. Emersing in water may remove the bloom that keeps the bacteria out of the egg. Candeling guinea eggs is also difficult as the shells are so thick.
If you want more guineas, i say go for it and see what happens.
Good luck!