From someone who's dealt with the UK Inland Revenue and the IRS, sometimes at the same time, as both a UK and US citizen and other immigration statuses, for many years ....
The short answer is that there's no tax issue for you, as you will not be resident here, and you won't be earning any income here. You'll be UK citizens on vacation (holidays) here and, in fact, you wouldn't be allowed to work here with a B1/B2 visa. The long answer is contained in one or more prior topics. Or, if you want to get the latest info, you can browse and search the
IRS web site, but be prepared to be confused.
One caveat - I'm neither a CPA nor a tax attorney, but have dealt with them and both UK and US based CPAs in addition to Inland Revenue in both countries on the "dual taxation" and related issues, which again won't apply to you. FWIW few CPAs in either country understand the issue you're asking about.
(CPA = US equivalent of a UK chartered accountant, or close enough).