I think so much depends on what they already understand. For some, they might just need to be prepared for th parents absence, the reason not even needing to be mentioned. Others might just need a basic explanation "daddy is taking a trip to the hospital. the doctors are goinv to help him feel better. we will have to take extra care of him when he comes home so that he can grow strong and healthy! here is what you can do..."

others will need to know more to relieve their anxiety. if they can absorb light details about the procedure an postop needs, then be clear, matter of fact, but positive. let them know how they can help and answer questions the best you can without excessive detail.

always let them know who is going to be caring for them, any changes in their routines, and help them practice hospital behavior, gental at home, and ways they can help.

Wishing you all the best with the surgery.