You might want to consult an electrician rather than some idiot in the home center.

First off, this cable is really TYPE USE-2 as far as the NEC goes if that helps you. You can run it both underground or inside (treat it like it was NM).

However, you can't use triplex and 4/0 Al is way oversized. You must run a ground with your feeders these days (there was in the past an exemption if there were not other metallic connections (phone, cable TV, metal water pipes, etc...) between the two structures.

Even figuring voltage drop 2/0 would be sufficient (though bigger doesn't hurt except the lugs on your breakers and panels might not take it). Without voltage drop a 2g wire would suffice.

Now we get down to the next problem, you wanting to run an extended run inside the barn. The problem here is that there is required to be a disconnecting means at the point the feeder enters that building (it can be outside or inside the building but it has to be a the point the cable enters). You've got three choices here:

1. Move the subpanel to where the cable enters the building and use it for the disconnect.
2. Route the cable around the building to where you want to put the subpanel and use the subpanel as the disconnect.
3. Install a separate disconnect at the point of entry and then continue on to the subpanel.

Don't forget the barn is going to need it's own grounding system (rods, etc..).

Actually plan to hire an electrician for most of the work but excavator is onsite this week putting in my water line and told me he'd could dig the electric trench and lay the wire for me all in one shot. So I was trying to figure out the burial wire so I could have the underground work done...just didn't want to leave it short for the electrician or on the other hand buy way too much wire...

I figured the Barn would need a disconnect and then different cable to the panel.

Can the buried cable be run in the house basement for the 90ft to the main panel or does that have to be something different?

It can be run inside. The rules for USE say that you can just treat it like NM (ROMEX) inside the structure. The feeder breaker in your main panel protects it.

They make a quadplex 2/0 quadplex (often with smaller neutral and ground conductors which is acceptable) in a USE that is what you want.

Make sure your trench is deep enough, 24" under most places.

Ok so had an electrician look at this but wanted to get other opinions to make sure I am not being sold a Porsche when a Chevy will do.

So the house actually has a 320 amp meter base already installed with one feed to a 200 amp panel inside the basement right behind the meter location. Basically all the circuits are currently filled except for 1 slot. His suggestion is the following...

Connect a second feed to the meter base and run it to a 200 amp disconnect mounted inside right next to the existing main breaker panel. Then wire to a new 200 amp panel on the other side of the basement closer to the where the line runs out to the barn. The second panel on this side of the basement would give us a power supply on the back of the house if we ever were to do a pool or other outdoor lighting. Then from this second panel with a 100 amp breaker run URD cable in conduit to the barn to a 100 amp disconnect on exterior rear of barn. Then wire from the disconnect to the panel location in the barn.

Any other thoughts or concerns?

I don't see anything wrong with that. If you're out of slots in the main panel it's probably advisable to do some sort of subpanel. His idea works for me if that new subpanel location makes sense to you...pool, hot tub, more lighting, outdoor kitchen....all could make use of that.

Ah wait a minute I got that one screwed up...

It is actually going to be two 200 amp panels side by side in the basement. Then a 100 amp breaker will be in the second panel to feed a 3/0 URD cable to barn. If I want a hot tub or pool in future I can run it off the second panel.

Will 3/0 aluminum cable even fit onto a 100 amp breaker...I would have thought its way too big for that...

Depends on the manufacturer. A 100A Square D QO is only good up to 2/0. I'm not sure why you need more than 2/0 anyhow.