The best combination I've found is to saturate the interior with ultrasonic units - at least one per room, since the waves don't seem to pass through walls - and use chemical sprays on all exterior access points.
I used to live in a basement apartment, and I had bug infiltration of all kinds, including spiders of many sizes and types, in my basement. Bug sprays on the exterior were only marginally effective. I started using the ultrasonic units, and virtually overnight I saw bug infiltration drop by about 90%.
I don't live in a basement apartment any more (now I'm in a third-floor unit), but I still live in a a wooded area with tons of insects and spiders. I've been using only the ultrasonic units and still gotten very little infiltration, but it's increased recently due to the summer heat, so I'm starting to add some chemical spray to the mix at the windows and other exterior access points. It's impossible for me to spray from the outside of the 3rd floor, so I'll have to settle for spraying the window frames from inside. I don't have kids or pets to worry about, so it shouldn't be a problem for me.
The trick with the sprays is to use them around any potential access point - doors, windows, cable penetrations, dryer vents, A/C vents, oil lines, and all places where wooden structure meets concrete, brick, or block. By using them only on the outside, you reduce the risk to your kids, but still give the chemicals a good chance to work.