Hi Ahmawa!
I'm not the best person to advise, because my family prefers autonomous education. I do know that alittlebitofstructure.webs.com/home-education-info is popular with my friends who use curricula, so you might like to have a look there.
Many British home educators use a pick and mix approach for the different topics, because you might find that you like one provider's history lessons but their maths programme doesn't suit your child, for example. One of the biggest mistakes which people say they made in the early days is investing too much money early on. It can take a while to discover what works best for your own child, and you don't want to be stuck with a stack of books which are all wrong for him. See what you can borrow or get on free trial first, or just buy the first book in the series. Local home educators will be happy to show you what they are using or may even lend you some of their books to help you decide.
Because one-to-one attention focused on your child's individual needs is so beneficial, you will find home ed more efficient than school, so you won't have to sit working for six hours a day. Most parents of under-8s do just a few hours a day of formal work at most (and some like me do none at all, but have our children learn entirely by following their interests). You also don't have to worry about your son "falling behind". For one thing, he will learn quickly when he gets stuck in. For another, you can go at his pace, so it really doesn't matter what his level is. Unlike at school where there are dozens of other children whose needs must be met and who can't wait for him to catch up, you won't have to plough ahead and leave him behind if he isn't ready!
Because of that, you don't need to have everything completely arranged before you start home educating. You can experiment, make alterations and add subjects in as you go.
A schoolteacher can't turn up unprepared on the first day of term. There is a curriculum which must be delivered, and besides that there would be chaos if all those children crowded into one room together had nothing productive to do. It's a different story for you. Even though you plan to have curricula in place eventually, you can still do a variety of things as you work towards that.
Suppose that at the beginning of September you still haven't settled on a maths scheme. You can keep looking for the right one while you visit a museum, let your son choose a load of library books for you to read to him, watch a history video, and try a birdwatching challenge. You'll figure out the maths plan in due course and you can start it whenever you're ready. That might be later in the month or later in the year. Education is a long game. There's no deadline.