parent in laws 37 year anniversary?

Okay im asking this here because this is where i feel the most comfortable asking anything!

So my in laws celebrated their 36 year anniversary this year, and last night i was think that over the past 3 years that i have been in their life's they have been amazing...okay amazing is not even the best word to describe them, when my husband was working out of town they would watch the children while i went for all my pregnancy appointments, they took me grocery shopping so i didn't have to take a bus, they did everything, my father in law even came over to take out the garbage and change the cat litter.

my husband is really close with them, he talks to his mom everyday for at least 2 hours, he helps his father out all the time, we are always there or they come over to our place for dinner. okay to get to the point, they had a rough year this year, with both of them having surgeries, and so forth, this years anniversary was the greatest, but we did pay for dinner for them, i know its not normal to have a huge celebration on a 37 year, but i really want to throw them a huge thing for their 37th anniversary, in a way to say thank you for being so awesome, and to also say that they have the most amazing love, and knowing them makes me believe in the power of love and working on a relationship ( i grew up much differently then my husband, i though when you have problems you walk away, you don't fix them.....)

so what im trying to ask is it okay to throw a huge party for a 37th year anniversary ( i plan on inviting a few people..like 30 or so) or is that something that should be left for 50 year?should i invite less and make it more causal, like just a nice dinner?