This is not a surprising reaction. As a matter of fact, it is entirely predictable. Besides, to do so would be to go contrary to the Word of God. You need to follow the admonition of 1 Peter 3, verses 1 and 2 where wives are told to win their husbands by their godly life-style, not by nagging. Perhaps the best approach with your husband is to gently remind him about what often happens on Halloween.
People put glass and nails in candy.
Stress the danger that children face on Halloween and how Halloween has become a time when people play pranks on one another that sometimes are dangerous. Police departments all over the country are reporting that there are a number of crimes that sharply rise on Halloween. The burning of vacant buildings, grass fires, the breaking of windows and the torture of cats, dogs and rabbits are becoming all too commonplace. Suggest to your husband that it is better to keep the kids home on Halloween then to expose them to what could possibly happen. It is not easy to be in your position and there will be struggles.