The definition of compliant is obeying. An example of compliant used as an adjective is a compliant student which means a student who follows all of the rules. complying or tending to comply; yielding; submissive.
We're having the ring bearer wear a tux that is age appropriate. It costs about $70, everything included. Your tux shop should have these or be able to order them. Edited to add: A friend several years ago had a ring bearer in her wedding and dressed him in a shirt and tie instead of a tux.
Money is the main factor in your wedding formalwear decision. Renting will cost about 10% to 30% of the price of a new tuxedo, and tuxedo prices begin in the $300 to $500 range. If you attend three or four formal events per year, buying a tux may be worthwhile.