3 and 4-year-olds learn from play. That's how they are wired. If you want to give them the best start, read to them, take them interesting places, do regular household activities with them like cooking and sorting socks, give them lots of free time to explore and experiment, sing songs, see live performances, get out in nature, let them fail at things and learn from it. If they love word games and puzzles, great but typically, those kids seek it out as opposed to being fed it. IQ is largely genetic and barring mistreatment and neglect, will develop as it's meant too. I have two high IQ kids and it doesn't make life easier for them... they just have different challenges. It doesn't make them better... they still have messy rooms and forget their school lunch on the counter. They still bicker with their sibling and do stupid things that embarrass me lol. They learn fast but I tell you, a kid with average IQ, a good work ethic and a love for learning is real competition.