The three bits of advice I have for anyone thinking about seeing this movie:
1. Go see it now before someone can't help themselves and spoils any of the significant plot points / twists.
2. Make sure you're up to date on the characters in the Marvel Cinematic Universe. This is not an origins story. There's no flashbacks to previous films. This is the sequel to multiple MCU series and it assumes you know who each of these heroes are.
3. (As suggested by Howard Tayler) If you're planning on taking younger children, you might want to see it yourself first. There are reasons why audiences are not exuberantly cheering on their way out of the theater.
And if you're sitting at the end of the row, feel free to hit the restroom rather than wait for the post credits scene.