It was initially a Greek term, but as was the fate of many Greek words, it wandered its way from East to West, and ended up as a Latin term as well. If you know exactly how many, you should use the proper prefix. One desperately looks for a term that is a collective, but which carries the meaning of an undefined number. There are English gems such as a pride of lions and a host of daffodils. Say, for example, that you have synthesized something in a biochemical mixture that contains three or four peptides.
Polypeptide is way too big.
However, an oligopeptide means that there are a few peptide units, I'm not sure how many. This may well be the most accurate description of just what you have. I love the British modesty that is shown by hiding a person's physical weight by referring to it with the dimension known as the stone. This is, as I remember, something like 14 pounds. So, if stones were the weight equivalent of 10 milligrams, the activity of TA would be several stone.