Unity will certainly do the job. It's quite powerful and versatile. It's not that hard to get into, you just need to start with the basics before diving into making an adventure game - that said, an adventure game would probably be one of the easier projects to make in Unity really.
The other advantage to Unity is ease of asset importation. It kinda just works with whatever you throw at it.
However, if it still seems a bit overwhelming, there's the excellent Wintermute engine, which specializes in 2.5d adventure games. http://dead-code.org/home/
My only problem with Wintermute was with asset importation. Could never seem to get it to read my 3d animations very well, but I'm a Blender modeler, and it was largely an exporter problem with Blender.
For adventure games ("Point & Click"):
I'm not a programmer and I've worked with them. However, you can get more out of them if you're not afraid to learn some simple stuff, akin to CSS code that graphic designers should know.
Adventure Game Studio might be a good option. If you want a showcase, I think most of the games published by Wadjet Eye are made in AGS.
There's also Wintermute Engine, but the development seems to have stopped now.
You may want to check out the Adventure Game Studio. I didn't try it in years, to be honest, but it was quite good back then and it still looks great.
Another similar tool is the WinterMute Engine but I never tried this myself.