I don't have any kids of my own, so I can't really comment on that part of it. My wife has 4 kids and the youngest lives close to us. The others are in other states. When he got married, she called all the shots, but didn't actually do anything. Her parents where part of the decision process, we where not included, or even told about anything until they had made all the decisions. They decided to have the wedding on our land. We where never asked if this was OK, we where informed. They said that they would do everything, they didn't. A week out, I asked when things would start happening, they didn't know. I ended up doing everything outdoors, and my wife took over all the indoor arrangements. Her son was clueless. He just wanted to hang out with is friends and my wife actually had to take him by his elbow, pull him out of earshot, and very strongly, told him to get off his butt!!!!
The day of the wedding, her parents showed up and her Dad became my helper. He was good as long as I was encouraging him to help me. Her mom was worthless. Her friends where worthless.
In the end, it turned out OK. We did what we had to do to make it happen. Neither of us where impressed with any of them. My wife is very honest about having kids. She says that they are over rated. I agree.
For both of us, it was a horrible day, but we pushed through it, and in the end, it was worth it. Neither her son, or his wife thanks us for any of it.
Now that they have a son, the same thing happens for his birthday. We plan it, we make it happen, and they sit on their rears and feed their faces. It's sad, but it is who they are. We do not offer them anything, or do anything to help them. They whine and complain constantly about not having any money, but the refuse to go back to school, or even apply for better paying jobs.
Do what you can to make the day as nice as you can, but remember that it's only one day, and soon, it will be just a memory.