As a father myself, I can only give you one piece of advise DONT DONT DONT...take your child to see this film... You will be much better off with The Incredibles 2. Also I'm not sure if there is a smaller/budget theater in your area, but if there is, I'd definitely recommend that. We took our kids to the smaller format theaters until they were about 5/6. For a couple of reasons..
1. As you mentioned, I don't think they could sit through a long format film
2. I did not want to be disrespectful to others who had paid premium price for a new film
3. I figured they would not remember, and I wanted their first *big time* movie theater experience to be a good one, they could remember fondly.
I mean for the record, my parents took me to see Empire Strikes Back in 1980, I was 4. We sat in the front row, and back then, the seats were literally so close to the screen you did get a crink in your neck from looking up. Also that blaring Mono soundtrack and sound effects from behind the screen in those days was pretty traumatizing
If you can be patient, I'd definitely take them to Incredibles 2 near the end of its theatrical run if you have such a theater in your area. besides the "bright colors" and happy music of Teen Titans Go may be more appealing to a toddler, but your brain will melt from it's sheer stupidity, and general lack of respect for common decency.
There are no more good TV Shows, only ones that haven't disappointed me yet.