Mulholland Madness is going to very likely be a problem for your husband, and Maliboomer might be a no-go as well.
DH is 5'10", and he's been between 280 and upwards of 330 on various trips. He hasn't gotten to ride Maliboomer yet. The reason is because there's a strap that has to click, and it goes from the bottom of the U of the shoulder harness into the seat. DH is about 1/2" away from it clicking, but that's still a NO.
He has tried Mulholland Madness exactly once. He could not ride.
Let me state that the CMs have been nothing but WONDERFUL. They are kind and discreet and lovely.
The guests near us at MM...not so much. DH has sumo wrestler legs, just tree trunks of muscle. If he had skinny chicken legs, he could have squished them down, and then the bar could have gotten down far enough. But he couldn't squish his lovely legs, so he couldn't ride. And the people were...ugly.
(what was worse is that we took the trip while waiting on a diagnosis for him...he came home to find out that he has a pituitary tumor that causes his body to make prolactin, which men are NOT supposed to have, because it's a nursing mother hormone...which caused his emotions to be as sensitive as a nursing mother...which means that unkindness on the part of the park guests was...extremely unwelcome. especially because it's exactly the prolactin that has CAUSED quite a bit of the weight.)
Other rides are fine. Screamin' was fine because they don't have the strap that Maliboomer does, though the harness is about the same.
Astro Orbiter is tight; I would recommend going alone on that.
editing...that was said before I noticed you have kids riding. DS loves AO, and I do not like spinning rides, but I end up going with him because it's just so awkward for DH getting out of the ride when he's riding with DS. So if you all go, you might want to get out as quickly as you can, so the child riding with DH can be helped out by you, without your husband having to try to get out with the child, if that makes any sense.
Especially for your tall husband, do NOT sit in the front seat for Pooh. That seat seems to have less leg room; sit in the middle or back row instead (which flies in the face of what your instinct would tell you).
If they seat you in the front of Splash or Pirates...be ready to be wet. My marathon-running skinny brother sat behind DH on Splash; they were in the first two seats...they were drenched to their undergarments. Thankfully for my brother, he was wearing clothes made of wicking material. Unfortunately for DH, he was wearing cotton, cotton, and more cotton. He was wet the rest of the day.
Your husband will likely NOT be able to take a kidlet on the "bumper car" ride in DCA...but you will. It's just a tight squeeze with longer legs, that's the main part...but it has a height requirement so your 2 year old might not hit the mark yet, which means you'll only have to take the 5 year old.
I definitely do NOT mean to make things sound all gloom and doom! The things that come to mind are the only things coming to mind. And most everything is fine.
But I would hate to NOT mention DH's experiences with Maliboomer and MM, and then have you angry with me. MM's line is *right there*, and everyone was watching DH get in and the whole experience...I don't think he'll ever ride it again, even once he hits a weight he likes better.
Oh, don't sit in the "cages" on Casey Jr. That's just craziness unless it's only your family. Sit in the seat 'cars'...just because it's more comfy and pleasant.
Lastly, do NOT be afraid to tell the CMs that you need two cars for something. The 3 of us split all the time. The CM asks how many, we'll say "2 and 1", and they know what that means. Two groups; one of 2, one of 1. Easy peasy. We could also say "group of 3, 2 rows please", but I prefer it like I said it first.
And remember that the CMs have been absolutely polite and kind.