What are good birthday ideas to do for my girlfriend?

I'm planning on doing something for my girlfriend and I haven't found something that I think will be great.

I was going to take her to Jersey for 2 nights, it's booking a hotel & staying there for 2 nights. We've had hotel booking on most anniversary days but I think we (me & my girl) have played out the hotels tho we've not done so for a while. I want to do something that she will enjoy with the presence of her family and friends there or something or something that I can do with her just us two. I don't want to only go for the norm "birthday sex". Or a meal. Or buying her Jewelry & perfume. I don't want that I want something well thought. And different please help. Her birthday is 4 months away. And I want to make sure I have saved enough for her birthday. Thanks in advance 😉