Small meals with snacks in-between are easier than three big meals a day. Don't pile food onto their plate. Children thrive on routine. Keep mealtimes regular and, even though its boring to you, serve them the same meal a few times a week with some variation, once you have hit on something they like. Usually they end up disliking it intensely.
Kids tend to eat up if they can serve themselves or help.
Little ones can set the table, call everyone to the table, wash and tear lettuce leaves, time the cooking with an egg timer. For every food, there is almost always a substitute. Don't ignore problems that interfere with eating, such as teething, sore throat, blocked nose, upset tummy. Keep offering new foods even if kids reject them at first. They need to see them several times before they look 'familiar'.