You will find this to be a mildly controversial topic among Muslims. Many Muslims believe that at no point should we, as Muslims, celebrate in any kind of Western holiday/event because there is risk that this is a doorway into accepting Western-ways and loosing the Muslim identity, incorporating Christian beliefs.
There is no right or wrong here. It all comes down to your intentions. Although most scholars would recommend against celebrating Western holidays.
For example, the biggest Western holiday, that you might be considering, would be Christmas.
Most Muslims, you will find, do not celebrate this holiday. The biggest reason would be that Christians will celebrate Christmas to remember the birth of Jesus (pbuh), who most believe is the son of God or God incarnated. Muslims do not believe he was born at this time, nor do they believe he was a God. To celebrate it would mean to celebrate a holiday that is against the teachings of Islam.
Revert Muslims are often stuck in the middle in that they have existing families who continue to celebrate Christmas. At this point, should you participate in the festivities it is to continue to build ties with your family and to join in on what is generally a very giving and rewarding holiday. There is no harm in joining them in their holiday but that doesn’t necessarily mean you should be popping a tree up in your own home and dropping gifts under it.
It’s really using your best interpretation of the situation. If you find that participating would be in the best interest of continuing the bond with you and your family than go for it; If it is infringing on your beliefs than help them understand why you can’t take part.
As for holidays like Halloween: Most scholars recommend you don’t participate as many believe it has a connection to Pagan origins and is a sign of idolatry.
Origins aside, many Muslims do participate in running around with their children, wearing silly costumes and trick or treating. Children enjoy time with their parents and that kind of activity should be encouraged. It, again, comes down to your interpretation and understanding of the activity you’re taking part in. Your Muslim children should be made aware that it has nothing to do with the traditions of Islam.
Most importantly we should put the traditions, of Islam, like Eid’s at the top of the list when celebrating with our family. When we take our Eids and make them the celebration, they are meant to be, they will far out weigh these other Western holidays and for the sake of the children they will rather their Islamic holiday over Western holidays.