It was a great movie for us both! He got an hour in before wanting Curious George. The Voyage Home has got a very solid message and is about whales. The movie is done in the tame, humorous, low violence 1980s style and has great visuals and lots of spaceships, but also, regular city buses, ships, and garbage trucks from San Francisco 1986. It's also full the relationship dynamics of the original Star Trek crew and the humor, and a little camp, underneath like some of the original episodes. There's Kirk the leader, and smooth operator with, in this case, Earth girls. There's Spock dynamic making us think about our humanity, and the crew's unique skills and diversity.
Sure, I grew up in the 70s and 80s, so it resonates, but it is also true that the content is more kid friendly then a lot of Star Trek movies.