How close should we live to our son and his family?

We love our son and grandchildren but his wife tends to be little prickly, and a lot of her goes a long way. We would like to live close enough to go to grandkid events, etc., but we fear we would be living in tension. She has also said she wished we lived close enough so they had a baby sitter. We raised our kids - we don't want to raise theirs. We want to be grand parents. Short vacations with them are tolerable, but we (and probably they) are relieved when it is over. Should we live closer and accept the tension, or live further away and miss seeing them but being outside that tense situation.