I know that the burkini does not cover the face. That is why it is a separate issue. FP's posts 260 and 261 both make mention of articles that are about the burka. There are others, just start there and read down.
I'm pretty sure that we can agree that Halloween is a special case. It isn't customary to go around knocking on strangers' doors to ask for candy at night, either, nor advisable on other days of the year. Actually, the older Belgium laws banning face coverings were made specifically to deal with the issue of covering the face during celebrations, carnival, so there is that banning masks on Halloween option, if you think it is a good idea, in the interest of fairness or something.
To mention the Belgian rules, again, they are specifically intended for use in parks and on public roads. Yes, the government has the right to require that those who use public facilities be visibly identifiable. They aren't going into people's homes and removing their burqas, or finding them at work to do the same. Personally, I would not be made to feel more comfortable if a group of men wearing full motorcycle helmets were to show up at the park and just sit there, wearing their helmets. Nor would their use of Halloween masks, out of season, make me feel more comfortable. Why should a bunch of women who cover their faces be any different? Am I to be sexist?