As a dad I have found being a parent very rewarding. Not only because of the love and joy having a family provides, but also for another reason, I can be a kid again!!! I have an excuse to take the time to fling marbles across the room, cover myself in colored shaving cream, make way too much flour and water, and just forget about adult reality. Here are a few ideas for you dads who just want a little time to play kid to kid with your children.
Remember, at all times, it’s the process of the game or activity not the final product that is enriching for you and your kids. Be in the moment and enjoy each minute you spend, don’t worry about where the project ends up. Keep it “open-ended” and keep it safe.

Boys- Think physics. Anything that moves is fun.
Girls- They love a story line. Follow her instructions and make the fantasy come alive.
Boys and girls are different, but do all these activities with every child. “Girl” stuff is great for boys and “boy” stuff is great for girls. Forget societies influence, princesses and football, they get enough of that elsewhere. Just let them play! 

Ramps: set a board, large piece of plastic, a sheet, or anything that makes a ramp, up on the couch to elevate the end. Lay on the floor with your child and roll marbles, cars, oranges, or anything else thats roundish, up and down the ramp. Try dropping them down the ramp from above. Put an empty cereal box at the bottom and try to make it in. To keep your mind going think about the physics, the ball rolls up, pauses and rolls back down, hits another and deflects. Momentum, de/acceleration, trajectory… You can explain it to the kids, but they don’t care, they just want to play with you! Just have fun and be a kid. 

Dirt: when was the last time you were really dirty, just for fun? Find a few magnets, some shovels and a small jar or container. The best magnets are cow magnet, long slender silver cylinders. www.stevespanglerscience.com/product/1407 Now go out and find dirt or sand and start digging. Put your magnet in the dirt and rub it around. You know what happens, iron fillings will stick to it and are a hidden treasure for kids. Start filling up the container with filings, it will be a project your kids will work on for years to come. While you’re out there with the shovel, try digging to China, build some mountains for army men, make a house and village for the pony. You can always add water! Just play and get dirty!