I would vote for tall shrubs over a mixed screen because it will look tidier, be easier to maintain and potentially require less bed depth/thickness. Consider that there may be places where the shade of trees competes for light so it would be good to select shrubs that tolerate sun or shade. Oak leaf Hydrangea comes to mind for the side positions. At the back line you might want something taller (Amelanchier, Viburnum, Lilac, Arborvitae, Euonymus alatus, etc.) There is a good chance that it could be tree-like, in which case it might need lower shrubs in the future to fill in the lower gap.

Would you use the shrubs along the entire perimeter or just in spots that block our direct line of sight to neighbors?

Also what about a mixed shrub border, in the event that a pest wipes something out...would that look okay?

What you do in terms of creating complete privacy vs. partial openness between your back yard and neighbor's is a matter of personal choice.

If you choose tried and true landscape shrubs, a devastating pest is an unlikely likelihood. Compromising an artistic statement based on this fear would not be worth it in my opinion.

I would plant a mixed shrub border that uses some evergreen shrubs and some deciduous. Bear in mind that such a border would be at least 12 feet deep with the shrubs planted at least 6-7 feet from the fence. You could place the evergreen (including perhaps some conifers) at the sightlines of neighbors you want screened, and deciduous in between.

A mixed border like this will vary in height, and depending on the shrubs you choose also in width, which would allow smaller shrubs in front to thicken the border. In place of the smaller shrubs, perennials could be planted in the bays. Also, you'll get a nice mix of flowers and berries if you choose well.

Several viburnums would be evergreen in zone 6, including cultivars of V. rhytidophyllum and V. pragense. Other large viburnums include the dilatatums (many cultivars) and V. sargentii 'Susquehanna'. For a very narrow conifer, look at Juniperus virginianus 'Taylor'. Another great shrub would be Magnolia stellata cultivars. Oakleaf hydrangeas, as Yardvaark mentioned, are indeed beautiful and would do well in light shade, but are not very tall--maybe 6 feet.

I am not a professional but it seems to me that 12 ft deep borders on 3 sides would negate a big chunk of yard which you might need for the kids (the swing set is why I think you have them). Could you do a privacy hedge in the back (hicksii yew, arborvitae or privet for example) that would terminate on each side with a large conifer then place mixed shrub borders on the sides which would vary in depth from say 6 to 12 feet in an undulating fashion. Maybe the pros could chime in with yeas and nays.