Is it appropiate for children or adults to dress up to go to church? Does this mean that they are more closer to God than someone in jeans?
People dress up when they head off to some special event. Their selection of clothing tells everyone whether they think the event is important to them or not. Jesus told a parable where this fact served as a key element to the story.
"The kingdom of heaven is like a certain king who arranged a marriage for his son, and sent out his servants to call those who were invited to the wedding; and they were not willing to come. Again, he sent out other servants, saying, 'Tell those who are invited, See, I have prepared my dinner; my oxen and fatted cattle are killed, and all things are ready. Come to the wedding.' But they made light of it and went their ways, one to his own farm, another to his business. And the rest seized his servants, treated them spitefully, and killed them. But when the king heard about it, he was furious. And he sent out his armies, destroyed those murderers, and burned up their city. Then he said to his servants, 'The wedding is ready, but those who were invited were not worthy. Therefore go into the highways, and as many as you find, invite to the wedding.' So those servants went out into the highways and gathered together all whom they found, both bad and good. And the wedding hall was filled with guests. But when the king came in to see the guests, he saw a man there who did not have on a wedding garment. So he said to him, 'Friend, how did you come in here without a wedding garment?' And he was speechless. Then the king said to the servants, 'Bind him hand and foot, take him away, and cast him into outer darkness; there will be weeping and gnashing of teeth.' For many are called, but few are chosen" (Matthew 22:2-14).
Even though the king sent out to call guests from the highways, good and bad, yet the king was upset with a man who came without wearing wedding garments. When asked why, the man was speechless because there really wasn't a good reason for his lax attitude towardthe prince's wedding.
The point of the parable is not to put emphasis on our physical dress, but to show us a point about the nature of the church (the kingdom of heaven). The church consists of people called out of the world. Those who respond to the invitation are most often the lowly people of the world. The intellectuals and the mighty people despise God and His Son, but the little people of the world are eager to please their king. However, God still expects His people to demonstrate appreciation for the invitation. We can't treat God's church as some casual, everyday thing which can be taken or left. "Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth" (II Timothy 2:15).
The reason that dress was used to illustrate this point is that for the most part, the things we chose to wear demonstrate our attitudes. They are our personal choice; and, therefore, they reflect our personality.
Yet on the other end of the scale, Christians are commanded not to judge others who come less well dressed than the rest. "For if there should come into your assembly a man with gold rings, in fine apparel, and there should also come in a poor man in filthy clothes, and you pay attention to the one wearing the fine clothes and say to him, "You sit here in a good place," and say to the poor man, "You stand there," or, "Sit here at my footstool," have you not shown partiality among yourselves, and become judges with evil thoughts? Listen, my beloved brethren: Has God not chosen the poor of this world to be rich in faith and heirs of the kingdom which He promised to those who love Him? But you have dishonored the poor man. Do not the rich oppress you and drag you into the courts? Do they not blaspheme that noble name by which you are called? If you really fulfill the royal law according to the Scripture, "You shall love your neighbor as yourself," you do well; but if you show partiality, you commit sin, and are convicted by the law as transgressors" (James 2:2-9). Christians are told to treat everyone who comes equally, regardless of their dress.
Unfortunately, I have seen both ends violated. There are people who think that because Christians shouldn't judge based on dress that they should push their "I could care less" attitude into their brethren's faces. And there are Christians who look down on a brother's poor dress without ever learning why they are suffering. Both ends of the spectrum are wrong.
The article "Dress Codes" addresses the problem of imposing standards for dress beyond what God requires. The article "You Can't Tell Me How to Dress" addresses the problem of purposely dressing to offend other people.
People who know me know that I generally wear suits and ties when I am preaching, not because I think suits and ties are required, but because people generally expect preachers to be dressed up. I want them to focus on the message and not me, so I will match their expectations to keep them from being distracted from the message. Yet, I have preached in blue jeans and in stocking feet on at least two occasions. Why? Because there was a big snow storm and I had to dig out my car. I left my snow boots at the door. But no one cared because we were all glad that we had a chance to assemble and worship God despite the storm.
I hope this clarifies the matter for you.