@PrivatePilot any resources you recommend for someone wanting to start with RC cars and heli? My son is 3 so too young but I’d love to at least try to spark these interests in him.
I used to have a few local hobby shops that were my go-to's but I'm pretty sure they're all gone. That said, I'm sure they're still out there, so hit up Google and see what's around. Of course, online is a huge option now as well...but when it comes down to "I broke something and need a part FAST", your local store is going to be your go-to, so support them.
Be careful buying used, there's a lot of bashed up old junk out there, some of which you may not be able to get parts for anymore. Do your due diligence and make sure you buy something you know has a good support system behind it and is popular so there's no shortage of ready parts at hand. It would be like buying a V-Star versus a Hyonsung - you know you're going to be parts for the Vstar anywhere and the support system is going to last decades even when they do stop making them some day. The knockoff Chinese stuff, likely not so much.
As for when to start, personally, 3 is too early. Kids just don't really "Get" things in the hobby at that age and you'll just watch them bash into things and wreck the stuff endlessly. I suppose if you have a toy grade RC car or something that they can play with while you enjoy your non-toy grade stuff, that'd be OK, and it does at least introduce things that way, but keep your expectations low.
Around 6 or 7 at the absolute earliest is when I'd introduce them to a non toy grade RC vehicle honestly, and even then you may want to wait until 10 or so in order to get a full comprehension of how to care for and operate things, and an appreciation for the fact "these things cost dad money so I should try to not destroy them". Remember, a lot of RC stuff out there can easily become a dangerous weapon so they need to be put in the right hands.
Watch this video, and particularly the bit starting at 1:50 for a prime example of being too young for a non toy grade truck.