I'm sorry that you lost your father. These memories and sadnesses keep coming up at expected and unexpected times, so "go with it" and don't try to push the grief away. There's no timetable on that.
Keep doing what you are doing - tell stories about him, what he did with the kids, what he did when you were a kid, where you went on vacations, funny jokes or stories he used to tell, what he would think of X or Y that the kids did (stuff they drew or built or said), etc. Make a scrapbook (regular or on line) to collect the memorabilia you have.
My son didn't know either of his grandfathers, and one grandmother died when he was 18 months old. He's now in his 20s. You'd think he'd know nothing. But if you ask him about them, he can tell you their funny expressions, what they liked, what Grammy said about him, how his grandfathers would have loved his construction and engineering skills, where they went on trips or served in the military, and so on. That comes with endless repetition over many years. But it's there, and it's embedded in his brain, and it will get passed on to his children one day. So in a way, memories are created and not just retained - he has no real memory of these people but he talks about them.
You'll know it when your kids say something like, "As Grandpa used to say…" or "Hey Mom, remember when Grandpa took you to the lake and you caught that huge fish?", you'll see the value of the time you spent talking about it for years! You don't have to do this every day or even every week, but consistently and periodically.
I'd also suggest that you save a number of your father's things for them - we have paperweights and old license plates and books and so on, a watch, some of Grammy's serving pieces and knick-knacks, souvenirs from their trips, etc. So do put things away even if it's in the safety deposit box. Even some old clothes can be dress up clothes or Halloween costumes, and it's a nice thing to do.