Grass versus trees? - order of planting

I have a landscaping project underway which will include a small orchard of 12 or so trees. The surface has recently been cultivated to a fine tilth.

I am now getting conflicting advice between Landscaper and Project Manager (arboriculturalist) about the order of planting:

One says the grass sward should be sown and established before the saplings go in - which would mean the trees are delayed until around Sept. The reason given is that "sowing would disrupt and damage the trees".

While the other says that the trees should go in first, and grass sown immediately after, and both then establish together over the summer months. (And furthermore, that there is no way that sowing grass would harm the saplings).

Which opinion / approach is right?

Thanks for alll advice ...

buy turf?

we always place any planting first, followed by the turf.

im interested to know which is saying which

Project Managers are always right.

Hi - and thanks for your quick responses.
I was being a tad devious - at present it is our Proj.Mngr (an arbori-whatsit) who recommends that the grass is planted 1st. The reason for my post was to establish if there was any truth in his assertion (ref. damage etc) or whether he was merely delaying this phase to suit his own agenda/schedule .. ?
I just find it very hard to believe that sowing grass would in any way be disruptive or damaging to newly planted 3yr old saplings ... ?!
Can anyone reassure me - for or against?
I really would like to believe our PM - but what started out as a 5-6 week project is now entering MONTH SEVEN - and his latest proposal would see it extended by yet another 6 months!!
Regards,
Exasperated of Edinburgh
ps Too large an area to turf ... cheaper to sow with meadow grass.

Well - a quick exchange of emails with Proj.Man today reveals that his true motive is indeed to favour his own schedule, rather than the best interests of my Project. So, we are having a 'summit meeting' tomorrow at which time we will probably part company with both him and Landscaper.

Hey-ho.

Thanks, everbody, for all your advice on the original issue. Much appreciated.

funny i had a feeling the landscaper would be right, and it would be the project manager that was the complete tit!