I shadowed for both my large and my small animal experience. The vet whom I shadowed (she does both small and large animals, but in 2 separate practices) was very willing, mainly because she has known me for a long time and knows that I am serious about applying to vet school. She has also made a comment to me in the past that she only lets people shadow her whom she thinks have a chance at getting in.
Anyways, because she knew me so well, she would let me do more hands-on type things when I shadowed. For example, I was allowed to restrain cats and dogs in the SA clinic, give shots of penicillin, take temperatures, do fecals, etc. With the LA stuff, she let me do a lot. Give shots, take blood, float teeth

(I was terrfied the first time I did it!), etc. However, most of the horses that I did these procedures on were either her horses or horses whom the owner had said I could do it. She was always very careful to ask the owner if they minded me doing a procedure on their animal, and most of the time, the owner didn't care and was like "Oh sure, you need practice for vet school!" lol
I think it all depends on who you shadow. Because I knew my veterinarian so well, she let me do a lot more stuff (while shadowing) than most vets would. Sometimes though, I would ask the vet techs to show me how to do more vet-tech type things (prepping for surgery, etc.) and they were always willing to show me. Moral of the story -- I think it all depends on who you shadow. If you can shadow a vet that you have known for awhile and they know that you are serious about vet school, they might allow you to do more hands-on things while shadowing. If you have to call around to try to find a vet to shadow, you might not get to do much hands-on stuff. Good luck!