I think you could go with a Moby wrap. They are a little complicated to get figured out (lots of fabric and wrapping) but comfortable. My main problem with mine is that they are pretty warm, and since I live in Dallas, I didnt find it great to go and walk around places with. I think it would work well for what you are describing.
My favorite carrier is the Ergo - which probably would not be good for this - its a better walk around carrier, and better for bigger babies, and pricey - but worth it.
Most slings are totally safe - you can google to find the recalled ones - and use common sense - if it seems like the baby couldnt be able to breath well, readjust him.
Good luck!