Three words...Crotch, crotch, crotch. Get a pair or two of biker shorts (the tight, tight ones). If you get 2, sew one pair inside the other at the legs, creates a little pocket. Practice your walking so it doesn't look like you have a stick up your ass. Will there be pat downs? If not, wear a thick pair of tall socks and put the smaller stiff in there.
Finally, do a search here on TS for stealth. Plenty of discussions on it.
Good luck..