SFMM and Knotts in Same Day -- Feasible?

I would echo Dutchman's comments. The immediate stretch of the 5 north of Knott's is a disaster due to widening projects. That stretch, from the 91 through the east LA interchange is backed up at all times during the day now, rush hour or no. Rush hour on that stretch starts at 2, but is already bad well before then. I drove it on Monday and kicked myself for not taking an alternate route (which was possible for my destination, not so much for the trip between Knott's and SFMM)

I would also agree that Atlanta traffic is routinely worse than LA, but that's not the topic here.

Do yourself a favor and spend 2 days at Disney instead. Find out which park is not hosting early entry for resort guests each day and go to that park.

You cant do justice to the two Disney parks in just one day, trust me.

My wife and daughter definitely would prefer two days at Disney without SFMM. They are wondering what they will do for a day at SFMM. I tend to get bored pretty quickly at Disney parks (the Florida ones anyway though I see no reason to think the same won't be true of the California parks). My son tends to be the same though will not bore as quickly at Disney as I do. The two of us would likely visit the Knotts and SFMM over the two days given the choice. So one day at SFMM and one day at Disney is something of a family compromise.

IMO, Disneyland is in many aspects superior to Florida's Magic Kingdom, I can't imagine being bored there. SFMM is definitely the thrill park, though, sounds like that's more like what you and your son would be into. But honestly, it's just so far away from where you'll be. My first time there (pre GPS assistance) I looked at the map and figured roughly it would be like driving from Columbus to Delaware or Marion. Nope!