You are probably thinking that you take enough pics of your kids and you don't need tips.
In case you need inspiration...
1) They love to pick up stuff - rocks, sticks, marbles, shiny things. Catch a profile of them leaning over to pick up a new treasure with their little fingers. And take a closeup of their fingers while you're at it
2) Eating. Especially the kids that LOVE to eat. If you have one of those, shoot their eating sessions, mess and all.
3) Standing next to or under the dining table. One day, they won't believe you when you tell them that they used to shorter than the table.
4) Tippy toeing to reach the light switch, or anything else they can't reach. You will look at that picture later and be glad you took it. They are at that stage for such a short time (pun intended).
5) Reading, by themselves or with you.
Need more? This is an ongoing series.