Many of the big theater releases these days are in IMAX, 3D or an IMAX/3D combo. Seeing a movie on the extra-big screen or in 3D can be a big thrill for kids, but just because a little guy or gal can sit through a kids' movie in a regular theater doesn't necessarily mean they are ready for IMAX or 3D. Trial and error can be pricey, so how can you know if your kids are ready for the full theater experience?
When it comes to deciding whether to 3D or not to 3D, there is some official data out there to advise parents. According to the American Optometric Association, most kids have developed enough binocular vision (using both eyes together to see something) by age three to be able to enjoy a 3D movie. There isn't any risk to their eyesight if kids see a movie in 3D before that age, but they probably won't be able to see it properly. However, being physically capable of seeing something in 3D and having the patience to wear 3D glasses for 60-120 minutes are two VERY different things.
One easy way to tell if your young movie fan is up for the 3D upgrade is to see how he handles sunglasses. My preschooler refuses to wear sunglasses even in the brightest sunlight, so I haven't even attempted a 3D movie with him yet. On the other hand, my 18-month-old daughter already loves putting on play glasses, so I have a feeling she'll be up for the 3D experience earlier than her big brother. For kids ages five and up, it's worth having a discussion to explain why the glasses are needed for this type of movie and see their reaction when you explain that the picture will look fuzzy if they don't wear the glasses for the entire movie.
IMAX is a whole other story. Many kids won't react any differently to an IMAX movie than a regular one, but some might be frightened by the supersized screen. It's not wise to have your child's first movie be in an IMAX theater, but if she's handled multiple showings in a regular theater without being startled, she's probably ready for the larger-than-life experience. In addition, those particularly prone to motion sickness might feel a bit queasy during an IMAX showing (3D movies can trigger motion sickness in those who are sensitive as well).
Many theaters offer free or low-cost family movies at certain points throughout the year, so contact your local theater to see if any of these showings will be in IMAX. My son's first experience with IMAX was at a $1 showing of Madagascar: Escape 2 Africa and I couldn't tell if he even noticed that the screen was bigger. It was great only paying a couple of dollars to find that out, though, instead of paying $20 or more to possibly end up in the lobby.
Ultimately, kids are unpredictable. One child might be totally ready for the full 3D IMAX experience at age three while others might need several more years. As a parent you ultimately know your kid best. Just remember to be patient and sit near an exit.