R2, R2, L1, R2, Left, Down, Right, Up, Left, Down, Right, Up - All weapons
Not a bad idea...
An even better idea if it's possible, this way you and your nan both have freedom.
However if none of these are an option, just follow the general theme of "keep yourself to yourself, avoid eye contact". Pen knives are a bad idea. A very bad idea. Especially with all the current concerns over people carrying knives for protection, it's probably the worst thing you can do. And if you're 6"4', you could beef up a little to make yourself look less of an easy target.
I'd leave my bike safe at home, as you're not going to be able to ride it safely when you get there, so there's not much point taking it.
EDIT: All formatting went balls up.