Firstly, hello and welcome to the forum
Secondly, tough luck. In most of the UK what you want to do is illegal and this forum neither encourages or condones illegal activity.
Thirdly, Loch Lomond (fortunately or otherwise depending on whether you live next to it and endure the numpties who trash the place or the byelaws that stop you and your family playing on your doorstep) is in Scotland.
Those aforementioned byelaws now mean that you cannot camp all along one side of the loch during the height of the season.
You really need to search for the Loch Lomond and Trossachs National Park and read up on the situation before you visit.
Lastly, best advice

get in touch with some of the Scots who post in Out and About in the area. They're good folks to chill out with

If you can get to one of their meet ups you'll get on the ground information that'll last a lifetime.
Oh, and the burns that feed the loch all run through lands with sheep, not good to drink from unless really, really necessary and you're careful about it.
cheers,
Toddy