Hello,
I haven't been diving in Cabo San Lucas for many yrs, But... I am in the Cabo Pulmo area frequently. July will be HOT. If possible you should go to Cabo Pulmo. The diving is easy, 5-15 minutes away, on pangas w/shade covers. There's lots and lots of sealife. Not much for brightly colored coral. Outside of Asia, I think the sea of cortez has some of the greatest chances of seeing the big and the small. Tropicals, sharks, mantas, rays, eels, lobsters, sometimes seahorses and octopus. Schools of jacks you can swim through. Giant groupers. You just never know what you might see. I love diving with Pilu. The website is
www.cabopulmodiving.com . I have heard good things about Thierry above, I have never been diving with him, but it is a small area and he is spoken of highly.
Regarding La Paz. Thierry is right, Espiritu Island would be a nice place for your family. The sea lions are a blast. I have been diving with the Cantamar for many yrs. I wish there was some other company options in la Paz, we have been out with all of them except Fun Baja. The cantamar markets to the Europeans and dive groups/clubs. So you may be on a boat with 20 other divers, (not fun) all from one diveclub. Not always a good thing. The reason I still dive with them is when they have had large groups they have put us on our own boat with only a couple of other divers, nice, but we get whatever equipement/wts or whatever the other boats are not using. Have had to wait for additional tanks to be filled. etc. and only get to go to closer sites due to the late departure, which we never know about in advance. Many of the La Paz dives are far so a fast or large boat is nice, you are gone most of the day. They can be exposed, open water, be accountable to yourself and your skills so you don't have to rely on others. I have to say, regarding safety, I feel the operations in La Paz I have been with feel "kinda safe" it depends on the crew. All that said, I have had some spectacular dives in La Paz, lots of life. Someone on this forum recommended FunBaja. I might check them out in the future, If anyone has experience with them, I would love to hear. La Paz is a pleasant Mexican city. It is not overly developed for tourist like cabo. It is a 3+ hr drive from Cabo. Nice drive though. Have fun, hopefully this longwinded post of mine helps.