Do the kids all meet all height requirements? If so, you almost certainly won't be able to do rider switch (baby swap). The point of the switch is so that a shorter kid waits with an adult while the family goes on, then the waiting adult can go on (with up to 2, I think, other people) quicker, without having to wait in the entire line, while the adult stays off with the shorter kid.
With coasters, from what I recall, only Big Thunder Mountain has a bench seat with one bar restraint.
Matterhorn, only 2 allowed in each car (one between another's legs). Indiana Jones, 4 or 5 across, each seat with their own seatbelt.
Space Mountain, 2 side by side each with own restraint.
Splash, no restraints, the back seat can hold two smaller people or an adult and a tiny kid side by side, but the rest of the log is one in front of each other, with a padded seatback between each person.
Grizzly, one big raft, one person per seat, each with own seatbelt, but it fits like 8 in the ride at a time.
CA Screamin' 2 side by side.
Mulholland Madness, never been on it, but from what I hear it's 2 side by side each with a restraint (used to be one bar restraint but I hear that's changed).
Things like Monsters Inc, Dumbo, Casey Jr, Pooh, etc, where there's just one bar or a big belt or no restraint, you can squeeze, but I'll tell you, the more people in your seat, the harder it is to see everything! Especially for the person in the middle!
All of your kids are old enough to ride (even line up) alone, and if you just tell the CM in charge of seating that you're altogether, they shouldn't put you on completely different parts of the ride. CMs have told us to tell them "x and y" for the separation in our party, since we generally split up the adults, and our 4 year old goes with whatever adult he chooses. (obviously not on the big coasters, LOL) So we say 2 and 1 or 1 and 2. Or on IASW and POTC, 3!
