What should I say to my dad?

Recently, my dad proposed to someone he has been dating for 8 years (ever since my mom and him were separated). We came out to colorado on vacation this year like we do every summer. The other night I told him after all these years how thankful I was of him helping me through the hard times in my life and being an amazing dad. My dad has never lied to me and never will and I know it so don't question that. This week his fiancee, who by the way I've only met 2 times before, came out with us. My dad has bookoos of money and my dad buys stuff for her all the time and I have a suspision that she is gold digging. Usually the whole family (my grandparents, aunt, uncle, brothers) spends time together at the cabin as a family, but this week my dad has been trying so hard to impress her that this isn't the case. They keep saying there's nothing to do at the house and my dad keeps taking them into town and spending all of his money on them. Also, my dad's fiancee and his daughter usually lock themselves in their room to go to bed early and don't wake up until late. I feel like this is a family vacation and we should spend time as a family. BUT! My dad is so happy with her and I don't want to ruin that for him. On top of that, my dad sucks up to them and does whatever they want to do and tries so hard to impress them that he has to go out of his way and try so hard to keep them entertained. IDK what I should say to him, I want him to be happy, but I also don't want things to be like this for too long. I will be moving out soon and right now my dads happiness is my number 1 priority.