Hi Kevin,
Yes the midges are bad. Some years worse than others. Since we are having a cold winter you might find that this summer might not be too bad. The spores get killed off if it is a particullary cold winter.
A lot of people who live and work locally (including the forestry commisiion) use a product by Avon called "skin so soft" the midges hate it and although you can still see and hear them buzzing around you they wont bite. You can buy products with DEET in them from any chemist, but they are expensive and full of chemicals, so we find the skin so soft the best option if you want to protect your skin.
Also by August they will be dying off - the worst time of year we find is early summer May/June and early July apparently they breed early in the summer and are at their most ferocious then.
They should only be out from around 5pm onwards so if you want to sit out at night then a couple of citronella burners work well in the awning. A farmer friend of ours uses bog myrtle which grows all over the west of scotland and a couple of bunches of that in the awning and I have never seen anything like it for clearing the midges away - but unless you can find somebody to tell you what you are looking for I would stick with the citronella candle.
Anyway, dont let the midges put you off, you have picked the best time of year to come, the schools will be back by the middle of August, you might get some rain, but you can expect that anywhere and you will have a great time.
Hope this is helpful - best wishes and have a lovely holiday.
Alison