SJS, Everything in life is petty but we must understand that materialism, if used the right way can have very powerfull effects and just the opposite, if used the wrong way will have negative effects. Let’s face it, 13 year old boys will not appreciate the mitzva to the fullest extent that even adults have trouble appreciating.
I’m not saying an axtravant, money wasting affair will have the right hoshpaoh. That focuses too much on the materialistic part. However, it is vital to show the bar mitzva boys what a special occasion this is.
If you go on vacation and spend money, buy your kids electronic toys etc., is this not fleeting? Even a nice house, while we look at it as it’s lasting, in reality it is not. Time passes by. We don’t live forever bound to our materialism whether it’s a house or car.
The feeling that you put into your kids by marking this occasion to the best of your ability is lasting. You are showing that this is important to you.
Let me ask you, will you make their weddings in shull too? You can make the chuppah outside. Not too many people need to come to the sheva brochos after the wedding, so how about inviting ten couples and doing it in your house? A wedding is certainly fleeting as well.
The bottom line is that no, special occasions don’t need to be big and ostentatious. In fact this downplays the holiness of such occasions as everyone is focused on shtissim. But still, we must try our best to make our simchos “real special occasions” by marking them ACCORDING TO OUR LIFESTYLE (that we can really afford to live – not on credit cards or charity), bar mitzvos included.