I attack with Bellowing Aegisaur and other creatures and they choose to block all of my creatures. 

Would I, as the attacker get to assign combat damage, and can choose Bellowing Aegisaur's attack to be first making its Enrage go into effect placing +1/+1 counters on my other creatures before their damage is calculated? 

Conversely, if I block with it can I ask them to assign damage in order and if they choose Bellowing Aegisaur before some of my other blockers would they receive their counters before their damage calculation?