If you have them they should wear them. If not, dress slacks with a shirt and tie are ok. If you need to buy them dress clothes look at your local second hand stores first. I've gotten some great deals on suits and blazers for my son at our local Salvation Army. I bought him a nice navy blue blazer and tan dress slacks right before Christmas and paid $5 for both. They both looked new.
That is an excellent idea; I didn't even thing of that. We have two that are local to where I live, so I'll be sure to check them out. Thanks for the suggestion.