Since she may honestly be expecting you to come across as intense and want to have a serious conversation, perhaps it might be better to do the opposite and start by being light hearted and while addressing some of the issues during the breakup may be needed, at least ensure that she has a good time and that stress isn't added onto her plate now or she wouldn't even want to consider the idea of getting back together. By letting her enjoy the weekend (and date with you so to speak), you at least 'show' her with your actions that you're capable of change and that you understand how stressed she is and you just wanted to help her unwind - which could work a lot more positively in your favor than having a serious talk.
Plus, it gives you the time to get past the initial unbearable phase of missing him and into a more even-tempered, secure mentality. Instead of trying to figure out signs your ex still loves you, you’ll be working on yourself and getting yourself into a better mindset. It gives you the space to say, “I don’t need him to be happy – I can be happy all on my own”.