Birthday etiquette question: what would you do?

I’ve got a big birthday coming up and I am planning my own celebration. I plan to take my closest women friends out for afternoon tea in NYC and will spend the day in the city with those who want to. I’ve talked with my best traveling buddy about staying overnight in a hotel and some others may want to do that too. Here’s the dilemma: I would like to stay in the expensive hotel that the tea is in but don’t want to ask my roommate to pony up. Should I rather book into a cheaper hotel where she is comfortable splitting it – and others might book – or should I tell her I’ll treat? (She has money but is less caring about luxury than I.)

I don’t have an issue going all out on this (it is a big birthday!) but I don’t want to come across as patronizing. Any thoughts?