Celebrating all festivals is got nothing to do with God.
By celebrating any festivals together, it just brings people together and strengthens their bonds with each other. By discriminating as my and your festivals, we are only creating borders and inhibitions towards other people. Isn't it?

The people of Paradise and the people of Hell Fire are not the same. In The Religion of Allaah we love Him above everything else, and we love those, who believe and obey Him, and we disassociate ourselves from those, who oppose Him and disbelieve. Allaah has only created us to worship Him. So everything you do has to do with Him, and you will be called to account for it on The Day of Judgement. And a person is upon the religion of his closest friend. If you have doubts about it, there are a lot of evidence in Qur`an and Sunna you can find the knowledge by searching about al-wala and al-bara.
Naturally hope for the guidance for non-muslims and wish good to neighbours and all, but Islam is not about following the desires, and pleasing the kuffaar. Still we have to be most polite and act righteously towards them, and have mercy on them, and CALL THEM TO BELIEVE IN ALLAAH AND HIS MESSENGER -SAAWS- and not associate anything as partners with their Lord. Thank you. If you are indeed a muslim, then read The Book of Allaah at least once in your life, and you will know all this.
May Allaah give us understanding, and prevent us from going astray to either extreme of either spreading misunderstanding and alienation from the people we were send to call to Allaah as a mercy, or by mixing with them and their actions, words, and thoughts and ways so as to lose our own Deen and our deeds becoming nullified. Äämiin. These are big things, and not small. Fear Allaah, and do your best, and be sincere in your intention, because every action is by intention. And Allaah knows best. Salaam