I have never heard of gifts at a bachelorette party. Ok once in a while someone brings a gag gift, but they are not normal or customary so no need to address that guests needed bring one. I also would not suggest there will be a "gift opening" because that would be suggesting they should bring something, whereas most people would not normally be inclined to do so.
In my experience and everything I've ever read or discussed, it's widely accepted & known that everyone pays their own way at a bachelorette, kicking in a little extra to cover the bride.
To be 100% clear on this, when issuing the invites (evites might be best, www.evite.com
) simply give the basic run down
"Lodging will be at B2B & my apt.
We will do some basic grocery shopping to accomodate home meals. Please inform me of special dietary needs in advance, or plan to bring your own special food if neeed.
Friday night the plan is to go to [local restuarant]. The average entree costs $XX.xx, and cocktails range from $X.xx - XX.xx.
Afterwards we will be going to [local club or whereever], the door cover charge is $X.xx per person, and drinks average $X.xx.
Transportation will be [are you cabbing it? Include the cost. Or public transport? Again include cost. walking? mention it so people can plan for appropriate shoes]."
Pad all prices by at least 10, if not 20%. No one is ever upset when a night out costs less then they budgeted for, but few people are pleased when it costs more.