sorry for the late reply but a late reply is better than no reply at all,
ok simply put you cannot go for several reasons.
first of all it is actually a matter of kufr akbar to take part in the religious celebration of the disbelievers, so xmas, easter, diwali etc are all kufr akbar to celebrate.
this is because as muslims we have to three fundemental principles we must understand here before deciding if it is allowed.
1. kufr bit taghoot.
kufr bit taghoot means declaring all systems, gods, faiths, philosophies, ways of life other than islam to be false. a taghoot is a false god, system of ideas etc. so laat was a taghoot, the trinity is a taghoot, democracy is a taghoot and everything that supports or goes towards it must be rejected.
and as muslims it is not enough to say here we only have to reject it in our heart, no our rejection is first through our limbs and then if that is not possible through the tongue and only if we are totally inable to act or speak do we say rejection in the heart is enough.
2. al wala wal bara.
another important concept, al wala is love for Allah's sake, loving what Allah loves. al bara is emnity for Allah's sake, hating and disliking what he likes.
so a muslim should try to avoid everything hated and disliked by Allah, should try to do that which is loved and liked by Allah. so which catagory does easter fall into? simple.
3. immitation of the kufr.
it is not permissable to immitate the kufr in matters distinctive to them, once again if taken too far this reaches the level of kufr akbar.
knowing these three points it is very clear easter is not permissable to you, even if it caused an argument, just talk back nicely with them, they are your parents but there is no obedience to the creation that is in disobedience to the creator.
and sister i know you are young, but i think just in case things go badly for you in the future i would talk to some muslim friends and their mothers and ask who can let you stop with them if you are ever thrown out, i hope this never happens to you, Allah willing but i have seen it many times dealing with new muslims so always have a backup plan so you are not forced into sleeping on the streets or other dangerous situations.