i don't think you'd need a ticket for the restaurant. as long as she isn't going into the room where the concet is being held, ur mom should be ok. i think they have a seperate door to the restaurant than for the concert hall anyways. there are usually still shirts after shows, and i usually buy mine after the concert. (the only time i've ever regretted that was when i went to see the Spice Girls in February and they ran out of like EVERYTHING.)
i didn't use will call for HOB, we just bought our tix when we got there. but i recommend using will call instead of anything else (like TicketFast) since will call is free.
also, this may seem like a dumb question, but what does TAI and WTK stand for? all i could come up with was maybe WTK is We the Kings. lol, sorry i'm not so good with abbreviations