Question about pp

I'm 4 weeks pp. As of tomorrow. Today I woke up with heavy bleeding like it was after I gave birth.. I called my doctor in a panic thinking something was seriously wrong. She asked if I was able to breast feed and I told her no I wasn't able to make milk at all. And now I'm bleeding. She told me it was my first period and my body was bouncing back quicker because I am not able to breast feed. Now my first born is turning 4 tomorrow and we have planed on taking her to the water park for her birthday on Sunday. Would it be safe to wear a tampon only for the couple of hours we are there. I don't want to be sitting in a chair away from her on her birthday... anyone have any answers for me?