Flossam, how old is your DS? Most high street opticians will test children from being around 2.5-3. Some are also able to do optometry tests, which are what you get at a hospital referral.Ask around at a parent and toddler group.
My dd1 has had a squint from being about 15mth old- one day it just appeared. Her left eyeball just totally turned into her head, so all you could see was the white part! It still does if takes her glasses off.
You may or may not need to go down the patching route- it all depends on why the squint has occured. For my dd, it's because she has a large degree of astigmatism and is severely long sighted, so patching for us wouldn't have had any effect. Having said that, when she wears her glasses there is very little trace of any problems, so much so we have difficuly getting her teachers to recognise she has some special needs.
I felt very similar to you, in that I didn't initially want to put glasses on her face, particularly after bad childhood experiences myself, but I'll never forget the first time she put her glasses on, looked at me, and said "oh, *hello!". It brings tears to my eyes even now.
HTH, feel free to cat me if you want to.