
Smile at your baby, preschooler, elementary child, or even teen. Have no agenda other than play. Let your kid set the pace. Let your kid be the leader. It's okay to let your kid "win," be more skilled, and triumph over you. Dominance doesn't have to exist in this game. Allow your guard and insecurities down. Be a kid the same age as your child. Be soft, fun, and playful.
What are the rules? Safety only. What is the objective? To have fun. Let your child wrestle with you. Let them smash you (be careful and don't smash them). Through in a tickle or a tease every once in awhile to remind you and them that there is no winner or loser, this is a game. It's about fun, bonding, showing your love, and building self-confidence and respect (not fear, but respect). It's about learning and teaching trust.Trust your child. Let your child trust you.
Only use strength to challenge your child some and to keep it interesting and fun. But never use strength to hurt them or "win." If your teen is stronger, be willing to accept this and build trust. Let them build their skills by teaching you. If you are uncomfortable wrestling with you teen, hold the pads for them and let them punch and kick. Let them teach you how to hold the pads and what to do. Remember you are not the "coach" right now. You are not the teacher. You are their helper. Let them be the coach. Just let them do and spend happy time with you. Even with your young ones, step back and let them be the teacher for a change. Life skills will blossom from both of you.
If you have physical limitations, it's okay. Work within those limitations. I am a mom with 6 bad disks in my neck and back. I just remind my sons to play softer with me than Daddy. I always protect myself and my child. The only rule is safety. Maybe the games look like wrestling or jujitsu, but you don't need knowledge of these sports to wrestle with your kids. The game may look more like horsey or may just be a big goofy hug. Remember, your kids will teach you and they will guide the game. Let them. They haven't lost this innate skill of rough house. As long as you are having fun, it won't matter. Don't take yourself or your child too seriously or it will become work. Enjoy yourself.
Here is an example for Toddlers
If you are still unsure, don't know what to do, or uncomfortable, visit a class with your child and we will help. We can teach you to play safely and keep it fun. We can teach you wrestling games. We can teach you how to hold the striking pads for your kids. We can teach you all how to stay safe.
My final recommendation is if your teen is stronger or more skilled than you and this bothers you, well it is time to enroll in a class with them. Some refer to this time as the "changing of the guard" when your child becomes stronger, faster, and "better" than you. If handled correctly you can build an immense amount of respect for each other during this time. However, never forget that you have more wisdom, and your child may still need your pointers once and awhile.
Some background about me:

Happy rolling, rough housing, and playing.