For sure that you don’t want your children to be called slobs in the dining room. It’s always best to start young when teaching them what to do and not to do when eating.
Establish basic manners such as washing hands before meals, eating only in the kitchen or dining room, chewing with mouth closed, etc.
Be patient with the little ones. Show them how to eat properly but understand that they may not be able to coordinate their fingers and hands in holding and manipulating utensils well yet.
You can have them use utensils specifically made for young kids to help with this. Provide them with the right utenstil for the right food. You may allow them to use their fingers for finger foods, etc.
Don’t get angry when they play with their utensils. Especially true for toddlers, this is the usual way they learn or practice how to hold spoons and fors properly.
Don’t forget to set a good example. Kids also learn fast when they imitate the adults around them. If you eat like a slob, then don’t be surprised when your kids become slobs too.