To sleep sack, or not to sleep sack?

Ashley • 31 yr old, legal professional and FTM! Hubby and I welcomed our baby girl 💞Kennedy on 11-8-2016. We love you pumpkin!!!
So I have an eight month old who sleeps in my bedroom in her bassinet that connects to my bed.  She starts off in her bassinet so I've been putting her in long sleeve, footed sleepers. However, she still wakes up in the middle of the night and I put her in the bed with me to breast-feed her and sometimes she ends up getting too warm while in the bed with me.  Although I know I will miss nursing her at night,  I was hoping to wean her off of night nursing soon and Just give her a bottle when she wakes so that she can stay in her bed at night. Once she gets in the bed with me, we both fall asleep and there she stays the remainder of the night.  My question is, sometimes she feels a little cold in her bassinet and I wonder if that is why she also wakes up pretty frequently at times at night. Is she too old to go into a sleep sack? I'm not going to use a blanket with her at night. But will she fall if she tries to get on her knees in the bassinet at night because of a sleep sack? What does everyone's little one wear to sleep at night and how old are they?