I am going to answer both your questions here!
My son is just turning 3 and we recently got him a Leapster Explorer, which he loves (some of the games frustrate him a little, but he's quickly picking it up and he loves the Leapfrog movies and the e-books I downloaded to his handheld). He also likes to play doctor (he's been giving his animals their flu shot using a block as the shot) so I got him a play doctor bag for his party this weekend. He also loves "cooking" for us, so I would recommend a kitchen and play pots and pans and play food (I found the $0.99 plastic plates, cups and bowls at Walmart and went to the baby area for plastic silverware-was cheaper than the play sets and didn have flower or girlie patterns for my sons :-) but the play sets will probably work fine for your girls). Also at this age, you can start buying board games-my son loves memory and he is getting uno-moo and hi ho cherry-o for his birthday.
My niece loved baby dolls and strollers/swings/cradles at this age-anyhing to pretend to be mommy. Your 1 year old will quickly like those also as your older daughter plays with them (my older son plays with his trucks and now his 14 month old brother wants to also so I went and bought big soft trucks so he could play with his big brother-so maybe get your younger her own baby dolls to play with her sister!
My 1 year old also likes blocks, phones, anything with music, his pull dog and books. He also likes pretending to eat when his brother makes him "food" so my friend got him a baby kitchen.
I want to get a marble set too, but I want to wait until the baby is a little older just in case.
Hope something here helps!