I have been lucky enough to have a good sized ditch that holds water most of the year and I feed the baby craw's to my smaller fish,but my half grown oscars eat all sizes. Even if the crawdad is big my 5 O's will gang up on it and rip it to shreds. If the head is not eaten by the O's my cat fish do a great job cleaning it out and I just fish out the remaing shell.
I have also taken large crawdads and boiled them and taken out the tail meat and shreded it up by hand and given it to my baby O's. I think by boiling it I'm reducing the chance of something being introduced into my tank from the ditch. When I boil them all the fish get to have some meat, even my angles ate it. If your crawdads are too big, I'd try that out.
The only problem with boiling them is trying not to eat them your self! LOL