There's deliberate lying to decieve and there's omission of the truth to protect
I avoid don't the former as much as I possibly can, but the latter is not only unavoidable, many times it is necessary.
after all, you couldn't tell you best friend you are organising a surprise birthday party for her, you can't and won't discuss personal and intimate details of your life with anyone, you won't be descrbing the last gory details on the latest bloody atrocities to your young children etc.
OP
I understand the dilemma but I agree with your DH. at 3 and 5 they are the perfect age to start learning to accept that you go see your parents now, they will do it later.
you could ask them to send a nice drawing to granny, spin it positively.
I had a MC when our kids were 7, 5, 3 & 1. All the questions I had I answered to the best of my knowledge, and tried to keep it age appropriate.
but when DS1 wanted to know about the ERPC and asked "Is that going to hurt baby? is baby going to get squashed? is baby going to bleed? " etc I had no choice but to answer him properly. there's no way I could lie. he was worried about baby so much that the more he knew the more reassured he bacame.
it was hard. still makes me well up, thinking just how much he cared.
but I know that being honest about everything was the right thing to do
my mum, dad and sister are/were always big on fibbing. I hate/d that. I don't see the point of lying to someone who craves to know the truth. And I always know when DM lies to me. we have a bad relationship because I just don't trust her.
It's sad.