i got all of my red eyes when they were adults or very close to it, however if you are sure you are getting cb frogs you may be ok getting smaller/younger ones. my experience is that you either get a hardy, healthy frog or you get a weaker one that doesn't seem to thrive quite as well and when this is the case it usually does not reverse and the frog eventually dies regardless of special treatment/feeding/housing etc. that being said i also believe that at least some of my red eyes were wild caught and that may have a lot to do with it. i think perhaps this is why some consider red eyes to be delicate--some seem to be but others are totally fine and thrive with no issues whatsoever. i guess the trick is lucking out and getting hardy ones on the first try. again, this is probably much easier if you get cb frogs to start with.

as a general rule you should have 5 gallons of space per red eye, so it would probably be best just housing 2 in the enclosure that you have.