Here are a few things:
Most HE parents find it reassuring to meet up with others when they first start, at least occasionally. Find out what is on in your area. You may be able to go chat with people now, to help you make your decision.
Don't ask anyone who hasn't tried home education whether they think you should do it. People have all sorts of odd preconceptions about HE when they haven't done it. I know I did! By all means do ask their opinions - but not about home ed! Ask them instead whether they have experience of children having the same type of school-related problems as your son, and what can help to resolve those within a school setting.
There are many ways of home educating. Whatever method you try first, you are likely to change to a different one later. In fact, you may try loads of different things. That's totally fine and normal. Don't stick with anything for long if it isn't working for your family. Experimentation is the name of the game. For this reason, don't spend much money at first. If you shell out hundreds of pounds on some all-singing curriculum and then don't like it, you'll feel stuck with it. There are plenty of free and cheap resources, as well as subscription services where you can stop paying when it stops being right for you!
If you are having a bit of a wobble, go somewhere interesting. Most kids love going new places and will engage with that. You'll see learning happening. And everyone else will acknowledge the value of it, so if granny is being critical of the home ed idea, then this may keep her quiet for a while. Teachers would give their eyeteeth to be able to take kids out of the classroom on a trip a few times a month, which HE families can usually do quite easily. If you want inspiration for where to go, ask around locally or, if you are able to travel further, ask us here.