Which edition of Lonely Planet are you consulting? Are you sure it wasn't Fodor's Guide?
From the 2017 Lonely Planet Guide:
"Scotland offers a range of child-friendly accommodation and activities suitable for families.
It's worth asking in tourist offices for local family-focused publications. The List magazine (available at newsagents and bookshops) has a section on children's activitiesand events in and around Glasgow and Edinburgh.
The National Trust for Scotland and Historic Environment Scotlend organise family-friendly activities at their properties throughout the summer.
Children are generally well received around Scotland and every area has some child-friendly attractions and B&Bs. Even dryish local museums usually make an effort with an activity sheet or child-focused information panels.
A lot of pubs are family friendly and some have great beer gardens where kids can run around and exhaust themselves while you have a quiet pint. However, be aware that many Scottish pubs, even those that serve bar meals, are FORBIDDEN BY LAW (my emphasis) to admit children under 14. In family-friendly pubs (i.e.: those in possession of a Children's Certificate), accompanied under-14s are admitted between 11 a.m. and 8 p.m. There is no clear indication on which is which; just ask the bartender.
Children under a certain age can often stay free with their parents in hotels, but be prepared for hotels and B&Bs (normally upmarket ones) that wont't accept children; call ahead to get the low-down. More hotels and guesthouses these days provide child-friendly facilities, including cots. Many restaurants (especially the larger ones) have high chairs and decent children's menus available.
Breastfeeding in public is accepted and is actively encouraged by government campaigns.
The larger car-hire companies can provide safety sears for children, but they're worth booking well ahead."
So please read the Lonely Planet Guide a little more carefully.
As you're going to be traveling throughout Scotland and England, you may want to consider the Premier Inn and Travelodge hotel chains. Most of them, especially Premier Inns, have family rooms, although the extra bed may be a sofa bed. Almost all of the Premier Inns have a family style restaurant attached, and are reasonably priced. Travelodge, if there is no restaurant attached, usually has a restaurant nearby. Also, if the youngsters enjoy McDonald's, they are everywhere in Scotland, and are somewhat more advanced the their American counterparts, in that they serve vegburgers.
Please check the website of each B&B you are planning to book, as some do specify that they will not accommodate children under 12 years of age.
As far as the midges go, the summer of 2018 was extremely dry, so midges were not much of a problem. We did encounter them on Rum, but that island is notorious for its midge population. We came prepared. Some of the outdoor stores, like Graham Tiso, Blacks, and Nevisport, have one size fits all midge hats, which only weigh a few ounces, and pack nicely in to a small pouch. They run about 12 pounds each. A good repellent, like Repel or Avon's Skin so Soft Insect Repellent, will suffice for exposed areas. Smidge is available in Scotland, but there mixed reviews on its efficacy.
You'll most likely encounter midges north and west of the Great Glen, and on the islands. However, the worst attack we ever encountered was in the hills outside of Ballater.
We took our son with us to Scotland at the ages of eight, 10, and 14, for periods of three to five weeks, and he was never bored. He enjoyed petting Highland cows, bottle feeding lambs, hiking, ferries, and watching Beavis and Butthead on television in our hotel rooms. We never had any problem finding accommodation, even in July.
Best wishes for your holiday!