left it too late to prepare soil for fruit bushes

hi,

have i left it too late to prepare the soil for planting blueberry, raspberry and dwarf apple trees this spring? it looks like i should have done this in autumn but i wasn't able to then and haven't been able to til recently. 

i have heavy clay, acidic soil - quite poor drainage - so was hoping to dig lots of organic matter into it (and maybe some sand) before planting this spring.

whats the best course of action now? assume the ground is/will be too cold to do anything with it now ?