So, I was in the same boat. Had 2013 BMW X5 35d, an excellent vehicle in every aspect except space. With second child on the way and the fact we do a lot of long trips, I figured big SUV is an answer.
Soon, I realized that I am not getting anything meaningful compared to X5, but losing a lot in driving dynamics. So, I decided to go Sienna way only bcs. engine 2GR-FE is pretty stout and 6 speed automatic is very reliable. Plus, compared to SUV's, they are much cheaper used. I needed AWD, that was a must, so SIenna was only option. Got 2015 with 42k, Limited.
I bought used in 2018, but under no circumstances I was going for 2017 and younger due to issues with 8 speed. Also, new engine, although on paper looks stronger, is in real life weaker at lower rpm's, and older engine is already very lazy at low rpm's.
How is it?
Family wise, it is an excellent choice. I would go with it again since is it super practical. You cannot beat minivan for family needs, and AWD, while super simple and compared to our Tiguan and especially BMW, not to be proud of, it does its job especially since I have snow tires on the vehicle.
Now, coming from BMW I never got over how cheap it is inside, that it rattles all around, that suspension regardless that it is soft, transfers more bumps than my 328i, that need like 10 miles for engine to warm up, and engine has useful power only between 4000-5000rpm for any vehicle passing etc.
It immediately had similar issues like my Land Cruiser in Europe. Brakes are not of highest quality and rotors will start vibrate if you are bit aggressive. Solved with EBC brakes. Battery regardless that it moves electric sliding doors, electric trunk etc. is actually smaller than in my Tiguan or 328i, which does not have electric trunk or not to mention sliding doors. Expect sudden death, which happened to me last fall. Upgrade battery capacity if you get it. Expect rattling windows, mirrors that move (there is way to fix it). If you get Limited like mine, you will have JBL system. If you like loud music like I do, consider sound damping as once you hike up music, everything starts rattle.
However, I am starting to think on trips to Home Depot it might be more useful than pick up truck. Three kids? Minivan is the only way to go.