Hi, I have an 8 yr. old daughter, 3 yr. old son, and 1 yr. old daughter. They all wrestle with daddy and mommy. Our youngest even gets in on it. We have been wrestling with our children since they could crawl. Daddy does it more than me because he's a man and I think they like that bonding.
My 8 yr. old seems to be the one who ends up hurt every time. She also gets really rough, jumping on his back, kicking, everything. My rule is if you wrestle rough, I don't want to heart it if you get hurt. You can then stop wrestling. My kids and husband love this time together and they usually are all ok. Your daughter peeing was just probably she had to go to the bathroom before it even began and the tickling just made it worse, but I wouldn't worry too much about it. After all it was an accident.
All of our wrestling usually takes place in our bed, so nothing gets knocked down or we throw all of the couch pillows on the floor and just kinda have a pillow fight and wrestle.