Impact when receiving a big bonus

Single income W2 family.  My base pay will be about the same this year as last, but 2 things have me wondering if I should updated my W-4.  The first is that I noticed on this year's return that I'm now getting a slightly lower child tax credit, or whatever it is, as my oldest turned 17 last year.  This was a surprise, and seems kind of random, but whatever.  The second oldest will be turning 17 next year, so it seems like at some point I need to increase my W-4 withholdings.  The bigger change is that this year I received a bonus that is roughly equal to my annual salary, and the same is likely for next year.  This was taxed, but I don't want a big surprise on my next filing.  I'd rather err on the side of getting a little more back on the return, than having to pay a lot.