Sawfish, should be fine, sounds very inert so no risk of scalding. Even slightly fresher and it probably wouldnt harm, spuds are very resilient.
A point if i may about the timing - I personally reckon it makes no difference how early they go in, after all, those spuds left in the ground all year after getting inadvertently forgotten or those voulunteer spuds always seem to do extremely well, and they've been in all winter! I think the plants sort it out themselves - when its warm enough they will grow, otherwise, they sit tight.