Is consistent disregard for students' time "normal" in undergraduate research?
No, it's not normal. You deserve respect like everyone else. Canceling on you repeatedly at the last minute is disrespectful. "Personal reasons" can happen once in a while, sure. (Although at some point you have to wonder what's real and what's an excuse.) However, department meetings are never planned at the last minute. We are all extremely busy, and if you plan something last minute, the answer you will get from 50%+ of potential participants is "I can't, I teach/have another meeting planned/am not even in the country that day". Me and most of my colleagues try to adhere very strictly to already-planned meetings, and those who don't acquire very quickly a reputation of being unreliable. If a professor has scheduled a meeting with you and decides to go to a department meeting instead at the last minute, it's insulting.
There are at least two possible reasons for the professor's behavior.
The first is that he has abysmal organizational skills. This can happen. Talking about it can sometimes help, but you have to be careful about how you phrase this. It's possible that the professor does not even realize that canceling last minute is terrible for your own schedule; some people are just self-centered and have a lot of trouble putting themselves in another's shoes.
The second is that you are so low on the professor's priorities, and the professor values you so little, that he doesn't care about inflicting this kind of behavior on you. This is not the kind of person you want to work with. Being busy and senior is not an excuse for being an asshole. But you are now reaching the point where you have to choose your battles. Do you want to complain to the professor and risk retaliation? Do you want to switch advisors and also possibly face retaliation or bad will, or work on something that is less interesting to you? Etc. There is a huge power imbalance between an undergrad student and a professor, so unfortunately I have to advise you to tread carefully.
You can adopt palliative tactics such as the ones described in Buffy's answer. But overall, no, it's not acceptable for someone to do this to you, and in an ideal world you would not put up with it. But we don't live in an ideal world. Academia has a bigwig personality complex, and many (not the majority fortunately) believe that they live on a superior plane of existence, wayyy above commoners, students, and underlings.
Some level of disruption is normal. The more intense the environment, the more disruption is likely to occur. As you note, much of this is unavoidable. Things happen in our personal lives that must be attended to (illness of a child, for example) and last minute meetings are outside the advisor's control.
But, you don't need to just go idle when there is disruption. If you have a good working plan with team members then you can probably carry on when a meeting with the advisor gets cancelled at the last minute. Have a five minute "conference" on how you can make immediate progress. The do that. Or... Make a list of questions that need to be answered before you can continue. Things like that.
When you do get to talk to them, ask for advice they might have on how to continue effectively when meetings get cancelled.
You ask if this is normal. Some of it yes. Some of it is also exacerbated by the fact that it is a senior professor who has lots of time consuming and constraining demands. I hope you aren't their lowest priority, of course. But learning can occur in any case if you just figure out how to keep the team moving forward.
No, it’s not normal, and your professor’s behavior is disrespectful and unprofessional. The fact that you are an undergraduate is not an excuse and does not justify treating you this way. I would suggest looking for a different research project to work on under another professor who treats you with the respect due to a junior colleague and a fellow human being.