The fuqaha’ differed concerning the validity of transactions made by a minor. The most likely view is that it is permissible in two cases:
(i) When it involves something of little value; in which case it is valid even if the child is below the age of discernment;
(ii) When it is done with the permission of his parent or guardian.
Items of small value are things like a loaf of bread or a piece of candy and the like.
It says in Mataalib Ooli al-Nuha (3/10): Except with regard to items of little value, such as a loaf of bread or bunch of herbs or a piece of candy and the like.
See question number 97489.
Based on that, if the price of these birds is low or it is being done with the knowledge of the child's guardian, it is permissible to sell them to her.
With regard to the money taken for admission to the hall, if it is in return for looking at the birds and animals, it is permissible because it is payment for a benefit, which is looking and enjoying, like the money charged for entering zoos, on condition that the time available for looking is known in general terms, because one of the conditions of payment is knowing the benefit for which payment is given.
If what is taken is in return for the possibility of buying, and they do not get to enter to look and enjoy looking, then it is not permissible, because this is paying money for nothing in return.
And Allah knows best.