Variation of Will…rnrb ...are solicitors right?

[Tingly]

Good morning

Are any of these options correct please as solicitors have advised option 1 , but i have doubts
Total net estate worth of deceased is 463k (house sold but prob worth 250 and is included).

Entire estate left to ex wife who they had a great relationship with (son is currently a bankrupt so didnt want to risk).
Variation of will desired to mitigate iht

Option 1
Am i right in thinking 325 can go to anyone , including the ex wife tax free?

And then 138k (using use of some of the 175k residential rate )to a direct dependent ie grandson Meaning that the ex wife maximizes returns without incurring iht.

OR

Option 2 (solicitors thoughts which i think might not be right)
Does it have to be
463 k net estate
175k to grandson
288 to the ex wife who then misses out a bit.

Thanks