Outside London I wouldn’t have thought that piskposkets would be that much of a problem. Also, IMHO, there is less of a problem with ‘scams’ than other European countires. I’m guessing you should be more vigilant on the routes to and from the airport tho’.
For your passport take a photocopy (colour if poss) of the information pages and carry that with you - leave the original in a locked case in your hotel room. UK citizens don’t have to carry id and I’m not aware that we expect foreign nationals to either (things may have changed recently but let’s assume you look like tourists and will be treated accordingly).
Wallet - I think the front pocket of your trousers/jeans is the safest place (if it is deep enough), you are more likely to feel a wandering hand and you probably won’t be absent mindedly leaving your trousers over the back of a chair in a pub as you might do with a jacket
Personally I often forget the whole wallet - especially if I’m going out of an evening - and take just the single credit card and some cash, the cash is split between diffrerent pockets. Mrs Hometownboy might want to make sure her handbag can be slung across the body rather than just off one shoulder if it means peace of mind.
The kids will be back at school in six weeks and English language summer schools will be over so you shouldn’t find the catherdrals crowded with bored noisy brats. Hope you have a good time and - please reassure the missus that the food has improved - for good British food you can’t do better than pub grub!
(ParentalAdvisory if you ever go to Barcelona you’d be amazed at the number of distraction techniques used by pickpockets. We’re not talking snotty faced Oliver Twist type kids but seemingly well meaning adults.)