Lompoc makes a nice half-day outing! The best time to come is May or early June when the few commercial flower fields are in bloom. There aren't very many flower fields left these days because farmers are finding vegetables to be more profitable. The best field is at Ocean Ave and Floradale Ave, where you can find multicolored sweet peas (which smell like heaven), bright orange marigolds, and purple lupine. The flowers look wonderful stretched out before you in rainbow colors with the mountains in the background and the blue blue sky. Kids will love to see them too! The other fields with vegetables and plenty of dust blowing around are ugly, so skip them.

An amazing thing to do is visit Lompoc when there is a scheduled rocket launch from Vandenburg Air Force Base. We saw SpaceX launch the Falcon 9 in January and June 2017 and we were surprised at how close the rocket was and how bright the flame. It was awesome! You can park by the flower fields for a good view.
If you continue on Ocean Ave you will come to Ocean Beach and then Surf Beach. From May to September, because of the protected snowy plover birds, the beaches are closed. It's worth doing the drive to Ocean Beach though, because the open road gives you a feeling of freedom amongst the fields of gold during the summer. Next, as you drive to Surf Beach, you pass a wonderful view of a lagoon (this is the mouth of the Santa Ynez River), a valley, a sandy beach, the blue sea, and railroad tracks passing through it all. You are on top of the world!
Lompoc is a windy place and it can be very cold on the beach and in the town so bring a jacket. Surf Beach is best for long walks. The surf is rough here and you can hear it pounding on the shore. There are sand dollars galore!
The town of Lompoc itself is pretty dowdy, though there are some sweet little Victorian houses with front porches and a gorgeous white Baptist church on H Street, just south of Ocean Ave. Here there are some wonderful trees that make an archway along the entire street. South Side Coffee, on South H Street, is a good place to go for a fresh apricot scone and a cup of tea.
Ryon Memorial Park, on Ocean Ave and O Street, is a nice place to stop to let your kids burn off some energy. It has large lawns, shade trees, and a playground with baby swings. The mountains surrounding Lompoc are pretty to see from this park. The Flower Festival is held here at the end of June, but didn't have much to do with flowers, which was a disappointment. The festival has carnival rides, food vendors, and good live music.
For yummy food, treat yourself to Scratch Kitchen while in town.
The best place in Lompoc that you absolutely must not miss is the salmon pink La Purisima Mission. What a sweet spot! It is a pleasure to spend some time pretending you live in the countryside, peeking at the sheep and little cute pigs, looking across large spans of golden wildflowers, walking the beautiful gardens full of silvery-green olive trees and a herb garden, and exploring the mission building, which is full of interesting displays.
A good hike to check out in Lompoc is the two mile hike up to Lookout Point, accessed at the very end of South Z Street. There is no shade on this walk.
A fun thing to do in summer is visit the amazing Lompoc Aquatic Center with kids. It is sheltered from the elements with a glass roof, and has large water slides. There is an area for big kids and an area for little kids.
Half an hour away to the east is the town of Solvang, a town with Danish windmills and lots of touristy trinket stores. For an amazing medieval playground in Solvang that will keep your kids happy for hours, check out Sunnyfields Park. Near Solvang is Los Olivos, a hip wine-tasting town.

Directions

The best place to see the flowers is on Ocean Avenue where it crosses Floradale Avenue, Lompoc CA 93436. Here you can pull off the road to the south on a small road and see the sweet peas.
The best time to see the flowers is early June (late June was not as good).
To get to Lompoc, follow Highway 1 to Lompoc (there are plenty of signs).
South Side Coffee, 105 South H St, Lompoc CA 93436.
Scratch Kitchen, 610 North H St, Lompoc CA 93436.
Lompoc Aquatic Center, 207 W. College Ave, Lompoc CA 93436.

Click on map for interactive view