Cows' milk and milk-based products provide a great amount of nutrition for young growing children. Things like food allergy, intolerance and personal choice however means that not everyone can, or chooses to drink it. Choosing plant-based milk alternatives can lead to deficiencies and growth impairment if nutrients aren't obtained elsewhere in the diet.
If you currently drink plant-based alternatives or plan to, it's advisable to choose varieties that are fortified and with at least 100mg of calcium per 100mLs. Avoid varieties with added sweeteners – even natural sugars (e.g. rice malt, agave), because our body treats these sugars in the same way as everyday white sugar.
An important thing to note regarding goats' milk – it doesn't provide very much B12 compared to cows' milk (B12 is a vitamin found mostly in animal products).
Also notice the protein content of rice and oat milk? It's not great.