Most IM brand races
(and some others
) have some arrangement to store "street clothes" bags
(usually one they issue you on which you attach or write your race number.
) They're fine for storing clothes and maybe a post-race snack, but I wouldn't put car keys, phone, or wallet in there--not just because of danger of theft
(which is actually pretty unlikely--who would have time to go through all those bags?!
) but falling out of the bag. I would leave valuables with your wife and arrange a post-race meeting place in advance in case she has trouble finding you at the finish.
(Longer races, especially big, crowded ones can be a bit of a crap shot--I finished my first HIM about 45 minutes faster than I had told my mom to expect, and finally located her asleep under a tree!
) Definitely don't leave anything of value in transition--again not so much a theft issue as things can get chaotic and it's easy for stuff to get lost or taken by mistake.
In the past I've often traveled solo to races, sometimes internationally. I usually leave everything but absolute essentials
(money to get back to the hotel, ID if I need to pick up my packet on race day
) in the hotel safe, and then secure the money and ID into an item of clothing with a zip pocket and leave it at bag check. On a few occasions, I discovered they did not have a bag check as advertised. I have done a half-marathon, an aquathlon, and even a triathlon with $ and my driver's license
(and, in the case of the HM, because it was required to enter the venue, my passport!
) in a baggie shoved into a zip pocket in the back of the top I was racing in. I don't recommend this. But those zip pockets, if you can find a suit or top with one, can be really useful in a pinch!