Unfortunately the predicting of midge activity is not that accurate. AS you will be aware this type of monster rely on water for hatching and hence they can appear anywhere near standing water. That could be a loch or it could just be an area of sodden peatland, neither of which are hard to find in the Scottish highlands. Hence the proliferation of midges in Scotland. A cold/dry winter helps. A dry spring and summer also help as fewer hatch.
How you will react to them is difficult to tell until you have experienced them. They are not like mosquitoes where you can squash that one in your room/tent and know you should be OK. They are more like a mist of niggling little bites which cumulatively can be annoying or painful and/or excruciatingly itchy. My wife is annoyed by them. I react very badly and scratch like mad resulting in sores.
The worst I have experienced was at a particular campsite on Arran but I would not deter you from visiting Arran. It is a most beautiful place and worth a visit with quiet roads great for cycling. We spent a few days there last year cycling in the south. As last year was hot and dry the midge population was down but the clegg population was up. (https://www.scotslanguage.com/articles/view/id/4801
) There is always something that will get you.
If you or your kids react to bites then I suggest you start taking a daily antihistamine about 2 weeks before you leave home and continue taking them until a week after getting back. Lots of people recommend Avon Skin So Soft as an anti-midge application. Works for some and not for others.
I would also recommend sticking to the south west corner of Scotland for your first trip. A number of reasons:
Bike hire should be easy in Glasgow
Arran is generally accessible from Glasgow
Arran is fantastic
Ferry from Arran (Lochcranza) to Mull of Kintyre (Claonaig) is easy - just roll up with your bikes
Cycling and scenery on Mull of Kintyre is lovely - quiet roads which are safe (hilly)
Easy to get back to Glasgow
Well away from the North Coast 500 (Google that for info) which is too busy for a family cycle trip IMHO
As far as the "west" is concerned that generally refers to the west coast of Scotland which is well known for its natural beauty and attractions along its entire length although west coast often refers to the northerly parts of the west coast. However Scotland is also beautiful inland both in the west and the east.