You want to shoot them not run them over!!
Only joking good for you, can you get the heads measured if they still have the velvet on?
No idea...i doubt it.
Never really thought about it as i never have submitted any.
I've never seen a roe in velvet measured but, as far as I am aware, it is allowed to remove the velvet then have the head scored.
The main scoring comes from weight and volume from memory but you will lose points for lack of colour.
I dont know which of the CIC official judges are nearest to you but it might be worthwhile giving him a ring and asking his opinion.
If you do want to stain the antlers there are various staining kits available.. I've never used any of them so can't say if they're any good.