Are there any animals that celebrate communally?
An event causes us to perform some sort of celebration that is motivated simply by joy and not any sort of survival instinct.


Celebrations usually mean large group activity but a play can be considered an event which is simply by joy and not any sort of survival instinct, and hence would fit your question. One can easily spot their pet playing around with objects when they are sitting around, busy in something 'boring' for the pets, like - reading a newspaper. But here it can be argued that pets have learned to do this to get the attention of the owner, and hence associated benefits. 

Well, plays of pure enjoyment have been documented in wild animals too. 


  I once observed a young elk in Rocky Mountain National Park, Colorado, running across a snow field, jumping in the air and twisting his body while in flight, stopping, catching his breath and doing it again and again. There was plenty of grassy terrain around but he chose the snow field. Buffaloes will also follow one another and playfully run onto and slide across ice, excitedly bellowing “Gwaaa” as they do so (Canfield et al. 1998).


Certainly, there was no motive here apart from having fun. 

I would encourage you to go through this article - Bekoff, M. (2000). Animal Emotions: Exploring Passionate NaturesCurrent interdisciplinary research provides compelling evidence that many animals experience such emotions as joy, fear, love, despair, and grief—we are not alone. BioScience, 50(10), 861-870.

Speaking of the celebration, such as - birthday, or the largest homo sapiens gathering Kumbh Mela, I would also be interested to know of some group of animals doing it periodically. 

Reference:


Canﬁeld, J., Hansen, M. V., Becker, M., &amp; Kline, C. (1998). Chicken Soup for the Pet Lover’s Soul. Deerﬁeld Beach, FL: Health.