An opportunity to create a new woodland - how exciting.
As you've had some advice already emilytree, I wouldn't want to contradict anything you've been told btu there's a couple of things I might suggest.
You don't say what sort of ground is to be planted i.e. rough pasture, wetland or rocky ground. Different substrates can determine the optimum tree species for the available land. Beech prefers a limestone or chalk substrate and is fairly shallow rooted. It is a good species to underplant as it bears shade well and will grow quickly under a planned shorter life species - even conifers.
I agree with your reservations about sycamore. Personally I would go for a nice broadleaf mixture including Field Maple (which will give you some lower branching and a squatter profile), Oak, Beech, Hornbeam, Lime with a Hazel and Holly understorey.
A couple of conifers wouldn't go amiss in the right place. A Scots or Corsican Pine will withstand the weather as individual trees and provide a contribution to the variety of available food to beast and bird. The deciduous European Larch can give some interesting branch forms.
Whilst I am on my feet don't forget a couple of crab apple trees.
I've lifted this useful link from a newsletter I got today. You might get some more free advice from the link.
MOREwoods is a simple scheme to help you create beautiful new native woodland – with advice and help from the Woodland Trust. In just 12 years you could be walking under the canopy of your own flourishing young forest of native trees; oak, ash, hazel, rowan. Native woods are a haven for wildlife and beneficial for our health and well being. In addition, they can also provide excellent game cover, produce valuable products such as timber and woodfuel, help with pollution control, reduce soil erosion and can make an important contribution to addressing the challenges of land management in the face of climate change.
MOREwoods is available to landowners throughout the UK with a minimum of one hectare (2.5 acres) but that could comprise a number of smaller areas. Contact alistairnash@woodlandtrust.org.uk for further information.
Good luck with the project and I hope your Dad enjoys his rather special birthday present.