Is using cross validation on your entire dataset acceptable when dealing with a small sample size
It depends, there can be different reasons to use CV: 


if you're using it to evaluate your model only, then it's fine to use the whole training set.
If you're using it to evaluate multiple models and then select the one which performs best (e.g. tuning hyper-parameters), then you shouldn't use the whole training set as you still need to evaluate the result of this tuning step on some unseen data.