I'm in a similar situation, so let me describe how we did it and maybe it will help. First I'll list a few things I think you need and then explain our thing.
- get one of the D&D starter sets, just stick to 5th edition if you don't have a preference. It'll walk you through things.
- get some cool monster miniatures and some miniatures for the player characters (PCs). You can find some nice pre-packaged ones for a decent price on Amazon... just look up "D&D miniatures starter set" and notice there is an "epic level starter" a "starter" and a "village raiders" set. The monsters in the village raiders are nice. You probably want to get at least one dragon... you can find them on miniature market, troll and toad, and amazon (usually pricier on Amazon unless you get the unpainted Nolzur's option).
- I think the starter set comes with a short adventure. If that goes well after a few sessions and you need more material, you can download the more advanced rules free from the wizard's site. And you will probably want to buy a "module" which is an adventure with all the hard work done for you... you just read along. Make sure it is for lower level adventurers.
- Module options: maybe even easier, is buy the one book that has many modules in it called "Tales from the Yawning Portal". It's "Sunless Citadel" adventure is well known for being fun and easy for a new DM.
Some explanation of how my family and I do D&D is below.
My 12 year old got interested from two things: Monster miniatures and the idea of leveling up to get more powerful. Oh, and some of his older friends played a few times and that got his attention.
He plays lots of video games, and leveling up is just one of those things that strikes a cord. Monster minis and D&D minis in general are just fun to mess around with... he likes picking a basic stat (Hitpoints or Challenge Rating aka CR) and then grabbing 20 of his favorite large or huge minis and then lining them up in order of "weakest to strongest". The fact that other kids had an interest in D&D made it seem more fun to him, though he'd rather play with me while he's learning the ropes.
He likes to kill monsters and doesn't give much care to the story or to dungeon traps (slows things down)... so I usually talk more story points to him OUT of the game when we aren't playing, and that actually goes over really well. But during the game, he is impatient. We basically started out with him and my daughter playing 4 characters total, but my daughter dropped out pretty quick and my son enjoys playing all 4 of the PCs because he doesn't have to wait around and he gets to learn a lot of the game at the same time. Too much sometimes, but making mistakes is fine... like Korvin said, just err on the side of the players.
Now my younger daughter has a slight interest, but she doesn't like blowing up monsters or whatnot. I think if we had started with a Catfolk / Tabaxi character sheet and mini, she might have been more interested. She "helps out" sometimes by helping me the DM roll dice or helping develop the story. She is an artist and likes to draw monsters from my various monster manual books. My wife doesn't really take an interest although she enjoys seeing me and the son having a good time and especially when we laugh out loud.
Last thing, you might find some ideas on reddit searching for "dad" under the /dnd section: