Since your Dad is wearing a PC I would consider renting one. Matt Newsome is located in NC and he rents PC's as well as full kilt outfits. You can check his site HERE. If he can't rent you an Argyll he can probably point you to someone who can

Please don't wear a sportcoat with the kilt. They just look wrong. The waistcoat is a possibility but only if you expect other guests will be coming without a jacket. If the men are expected to wear a jacket and tie (semi-formal) or more formal then a waistcoat is not appropriate. If you don't think you will be needing a formal jacket other than for this event for the foreseeable future renting is likely your best short term option.

Of course if the invitation is (semi-formal) the PC is a bit dressy (an Argyll is perfect) but you will look good. Another option for semi-formal would be to hit the second hand shops for an inexpensive tweed jacket and then have a tailor convert it for you. Personally I would go with the PC to be on the safe side. Do a conversion when you have the money for a second choice in case it doesn't come out as hoped.

Yes your cream hose are fine with a white shirt if you go with a PC or a conversion. There are members on the forum who prefer coloured hose, but I would rather see you put the money into a jacket than worry about the hose since yours would be appropriate.

As far as the tie if you go with a PC you get a black bow tie. If you can find an Argyll or if you do a conversion you can wear the matching tie you already own. Not my favourite choice (I prefer solids as well) but it is acceptable so spend the money elsewhere.