If it's to help your kids I would try to stay on their learning curve. They'll be doing things like number lines and numicon that you probably never learned. Learn it their way, and your knowledge will be more useful to them, plus it's probably better at building a fundamental understanding of the building blocks than how you were taught.
I can't recommend a book personally but something along the genre of "Maths for Mums and Dads" or even maths books aimed at primary school kids, might be a good shout. Are more adult resources actually better, or might you as well get the Usborne Book of Times Tables (which is lovely btw and really helpful at aiding understanding) and look at it yourself before you give it to the kids? I hope you don't take this as patronising, I genuinely think it is better than taking a sheet of times tables and trying to learn them straight. If you can picture the page with the bunches of bananas for the 6x table, your brain will hang onto it infinitely better, and when your child is stuck on 6x6 you can remind them to think in bananas.
Kjarten Poskett wrote the Murderous Maths series which is superb at explaining mathematical concepts in a really accessible way. I don't think Murderous Maths is exactly what you're after as it deliberately goes much wider and more advanced than the national curriculum but I would look at what else he's done.
In terms of helping your kids, in the early days a lot is about helping them get to grips with the real basics. Get some clicky blocks or improvise with counters or bits of pasta. We even had numicon. The more they do IRL with physical objects in their hands, the more they will embed the concepts. Don't push them to abstract it, push them to get physical objects out and move them around in space, or if they are a few years older to go back to a number line. I would try to do this stuff with them and learn number bonds, number lines, crossing 10 etc along with them. New maths. You don't need to remember your GCSE old maths to do new maths.