Vl D.
Yelp
Misnamed as a "San Diego" museum while being tens of miles away from the city, this is many things in one. The indoor and outdoor spaces are not large, but accommodate many things that actually can be "discovered" and played with multiple times during repeat visits. Good for age range of toddlers (dedicated space) to 8-year-olds. Few installations, notably the gravity run for wooden balls, will provide entertainment for mechanically inclined 11-year-olds, but they might eventually become bored - if not, you might have a future engineer on your hands. The indoor space is airconditioned, in the outdoors one would face the regular, hot in the summer, Escondido weather.
Many features might be better explored in a small group; the layout of the museum is conducive to interactions with other kids, so the visit will go better when the kid is bringing a friend or is able to strike an instant friendship (this is the enhancement, not a mandate).
Admission, at about $11 per person, is not very expensive. If you are a local, a membership ($30-40 per person annually) might provide a good value. No food or drink is sold inside, so bring your own snacks (your kids will have to eat outside). Parking is free.
Overall: worth a visit if you live within, say, 15-minute drive radius. With minimal assistance from the parents, the kids will be entertained for many hours. Tip: at the first glance, the museum does not look terribly exciting, but the smallish space is well thought through and will grow up on you and your kids.