Let's see...my parents was 3 years ago.
We didn't originally plan on throwing a party because instead my mom thought she wanted to just bring us all down to Florida and rent a place for all of us for their anniversary in November...And then she went to her brother's anniversary party and decided she wanted one too. My mom may have turned a little bridezilla. She sprung this on us about 9 months prior to her anniversary (and only 6 months away because we had to throw it before they left for FL). So, we didn't have a ton of time to save money.
Our theme was beachy because they winter in Florida and summer on a lake. Made the invitations ourselves using one of those sets that had the printable vellum. We used a picture of them walking hand in hand on Marco Island. We used lots of blue and gold and beachy accents. We had leis from Hawaii instead of a corsage/boutinerre for my parents. We had a ton of pics strewn throughout the hall.
We did an imovie with stills from their whole marriage; for some reason my parents had a gazillion slides and my siblings and I spent hours combing through those looking for pics to use. I did try to use a combination of silly/funny and serious pics and music because, to be honest, it can be a little overwhelming when you notice all the people that had passed away. I also made a real effort to include at least one pic of each person that attended--excluding me, my siblings and our families-- there was about 150 people. It was such a hit that everyone asked to see it again. Lots of laughter and tears.
Let's see, we did some of the cooking ourselves, but we also had a family friend that cooked a majority of the food and served, cleaned up, etc. We did do a buffet because our setting was very casual, at the social hall on their lake. As far as alcohol, we did have a pretty substantial bar--we're from WI, what can I say--and my 3 brothers did most of the bartending. In hindsight, I'd probably just have stuck to beer, wine, soda, water and coffee, if only because some people did ask for some crazy drinks. I am glad we decided not to do all the work ourselves, but we did not have the budget to support having it full-on catered either. My mom really wanted a more formal catered meal but we did not have the budget for that. And, she did not want to contribute.
You need to understand, my mom is a hoot. For example, at age 75, she went to her first Jimmy Buffet concert and loved it, so she wanted this to be a real party. The problem was we started the dancing part a little late (7, I think), and the older crowd wasn't much for staying out that late. So, in hindsight, we should have done more of a lunch thing instead of dinner, with dancing in the late afternoon. But, it did turn out to be a great family party for us. The d.j. said it was some of the most fun he's had. And it did look beautiful with all the candles, etc.
We did the bubbles for the first dance and gave the kids sidewalk chalk to write their own anniversary greetings on the sidewalk...quite a few adults got into it as well.
We made a terrible mistake by not hiring a photographer. My mom's brother died 4 months later and we did not get any pics of my mom with him. Also, we didn't get any family pics, and that was a shame. We do have our own pics and those taken by others, but I def. would have changed that.
Let's see there was some serious quibbling about money at times...we all did pitch in the same amount; however, that was probably a little unfair because a couple of siblings did absolutely none of the prep work, and it would have helped our budget if they'd pitched in more. So, you really need to figure out what your budget is and exactly what you will spend it on. Stick to it otherwise there will be hard feelings. For example, one sister decided we should have favors....well, that wasn't in our budget and that she got cranky because she felt she spent too much of her $. I'd also make sure you have one person in charge of the $ and keep all the receipts. I then made sure to give a spreadsheet of expenses to each sibling--just to avoid any potential conflict.
We did do save the date cards. Just the cheapos from vistaprint and that was fine for our purposes. For the invites, we didn't include response cards...maybe that was cheap but we wanted to save a smidge. So, one sibling was in charge of the receiving the emails/phone calls.
So, I guess these are my recommendations: decide on a theme, establish a budget, decide on roles (who will do what), figure how involved your parents will be, create a timeline and stick to it....I'm sure there is more, but I can't think of it.
Overall, it was great fun and my parents were really very pleased with the whole thing.
One thing that they did was take gold framed mirrors & clean them really well & use them as serving trays. It looked awesome! Truly a Martha Stewart moment. 
