Hi
My dd (3.9) has a Broviac line, and although it's not a portacath I thought it might help to post about it anyway, since they are similar.
Because my dd's need for the line is lifelong (it's for TPN (nutrition)), we've been through a few. She's had line surgery now about 8 times.
First some reassurance, I hope. Our experience is that scheduled line surgery (as opposed to emergency surgery) is usually quicker and more painless, because she will have an experienced surgeon. The tunnelling (to put it under the skin) does result in some pain but my dd has always coped with Paracetamol and ibuprofen. They inject some local anaesthetic into the area during the op, although always good to discuss this with the anaesthetist before to check they will.
There maybe a surgical nurse specialist for the ward, who you could phone and speak to. This person will be trained to describe the procedure and the portacath device. He/she might be able to show your dd a device so she can see it and handle it.
I would def suggest you discuss the location with the surgeon, they may not be able to locate it where you would ideally want, but having the conversation would def be good.
I hope things go well with the op. If there's any opportunity for your dd to get to know someone else with a portacath this might help her to adjust.
One final thing I would mention is that if, afterwards, you have any concerns about infection of wounds etc to go back in and keep asking until you are happy. I have found this aftercare lacking and we've had complications previously so do trust your instincts.