Men growing up is never easy..........in fact we often fight it It sounds like this party is more his friends thing then his, but something that does appeal to him which is natural. It sounds like he has come a long way in the last year. A business, a house a wife, those are all big changes and good changes. It sounds like he has worked hard to get where he is and is asking for a little bit of fun. Keep in mind that men hate to lose everything of their youth including the occasional party.
If you force him to stay home.....or make him feel guilty he is going to resent you over time for taking what he looks at as his youth. It looks like he is the man you married, he has done everything by the book and is asking for a chance to go be a guy once in a while. Which is pretty normal for most any man regardless of nationality. All men want to have a little fun......and this is his kind of fun.
Try putting the shoe on the other foot, if you were working hard and succeeding in life and had a chance to do something that you really enjoyed.....even if it was considered childish by him would you not want him to be the bigger person and let you do it?
I would not be worried about it at this point, he has come a long way and is working hard to be the best husband he can be......while still trying to hold onto a little bit of himself. The last thing you want is to take away the individuality he has for himself as this is going to cause him to have regrets in life.
Being a good husband, businessman and member of society is not easy for any man......allowing him a few treats once in a while is what makes you a good wife. Keep in mind that marriage is about give and take, he has given a lot.....now it is your turn to give a little and let him have a little bit of fun after all his hard work.