Im with everyone else, try and keep the eldest's routine as much as possible, and involve them. The best advice I got was to ask Miss M things before I did them . ie: I would say to her, 'hmm Miss H is crying, do you think we should change her nappy? can you help me by finding her nappy?' etc. It worked really well. From day one Miss M was there to help me. From helping me with nappies, to testing the water temp for baths, getting face washers, finding her a blanket, toys... anything really. The more we involved her, the more she wanted to be around her. Even on the car ride home from the hospital I asked how Miss H was doing, and she would look over to check on her....
hth