Yes, you can use a piece of conduit to protect the romex getting it in and out of the buildings and then to get the DB cable into the ground. Of course UF can probably be run all the way back without spices, it's generally permitted indoors everywhere romex is.

Yes, a MWBC explicitly counts under the exemption for the separate structure having a grounding electrode of it's own.

If the floor of the garage is at or below grade, don't forget the requirement for GFCIs.

Use 1/2" PVC conduit and in it run THWN #12 with black, red, white, and green wires. Where the conduit exits the house and enters the garage use an LB.

Here is a link that might be useful: LB

I'd much rather use cable.

Also, If I used an LB on the outside of my house, I would have to put a splice box in the middle of the dining room wall to transition from Romex to THWN. Unless I ran pipe all the way thru the house lol.

You know that rigid an intermediate metal conduit only needs 6 inches of cover, and UF is 12 inches if it is GFCI protected and 20 amps or less.
See table 300.5 and the notes.

The cost of some rigid metal conduit allowing 6 inch cover is well worth the few $$.

Or you can dig a 12 inch deep trench all the way to the garage.

It's not flat ground, it's downhill and there are many slopes on different angles.

It'll be easier to pay the neighborhood kids to dig the extra 6" than to deal with pipe.

"UF is 12 inches if it is GFCI protected and 20 amps or less."

Good to know, I was planning on going 18" but for the cost of a GFCI breaker I'll only have them dig 12", thanks!

"and then use a piece of PVC to sleeve direct burial cable to the ground, then run the cable into the garage"

whether you use PVC or EMT or Rigid you are not suppose to sleeve any kind of electrical cable, use individual conductors.
If you use a weather proof box on the side of the house for the transformation you could use a GFCI receptacle instead of a breaker.
FYI - the metal pipe will rot, rust and corrode very fast.

"whether you use PVC or EMT or Rigid you are not suppose to sleeve any kind of electrical cable, use individual conductors"

Can you quote that from the code?

There are instances where you can sleeve cable for protection.

It is perfectly fine to sleeve the cable with conduit per the scenario you have mentioned.

I know you have many comments against using pipe but I must recommend that you do so anyway.

The biggest pain of the project is the digging so why not use the pipe. It will allow for future addition of more circuits, easier for repairs if the cable was ever damaged etc...

Either way you wouldn't have to use an LB - you can trasition from the interior NM cable to either UF or THHN inside of the outdoor box you mentioned in the first post.

"whether you use PVC or EMT or Rigid you are not suppose to sleeve any kind of electrical cable, use individual conductors. "

so you're saying that pulling romex through any sort of raceway is illegal? Sorry but you are wrong, there is nothing wrong with what the OP stated here.

what you first posted and planned is perfectly fine. Just check with your local AHJ to make sure they aren't going to make you do anything special. If you pull an MWBC (edison) circuit, you will be required to put both circuits on a common throw breaker such as a double pole for example. So that both circuits are either open or closed at the same time.

jmvd20, after the stub up on each building I only have 180 degrees left. I'll use that up in 30's and 45's real quick, it's a treacherous run.

PVC Conduit will easily make gradual bends inside of a trench without using fittings to accomodate changes in slope etc... - or is this run even worse than that in terms of the grade changes?

"It's not flat ground, it's downhill and there are many slopes on different angles."

My first plan was to bring a hotbox home from work and run it in 3/4" PVC, but there would be too many bends and too much work. Much easier to just lay the cable in the ditch.

Gotcha...

I just don't enjoy the digging part so I always try to use conduit.

Since you're going through the work of trenching, why not put a 240V, 30A (or larger) subpanel in the garage?
If the added cost is within your project budget, it could be a worthwhile consideration for future needs, as well as add to resale value, if that is important to you.

To quote the OP:
"I'd like to avoid setting up a subpanel and doing the ground rod thing, this is just for some lights and battery chargers."

I would agree with you. That much work and I'd put in a 60A sub for the future. The "ground rod thing" is easier than the trenching. And he wants to pull cable through conduit, not individual THWN wires. I don't think he realizes how hard it is to pull cable. Live and learn.