Only you can answer if its worth it to you.

However, your assumption should be that if you don't pay, then you won't be sitting together. As noted above, AC won't separate young children from one adult, but you should assume that you'll all be as completely separated from each other as that allows, and probably all in middle seats.

If that's ok with you, then don't pay - and you might even get lucky with the seats. However don't assume that you will - and if being separated is a concern for you, then I think you'll have answered your own question about whether or not the price is worth it.