Are there any kiddy concerts playing anywhere near you? Tickets for the big girls could work - even just movie tickets. We haven't taken Nat to the movies yet (and she's 4) but I think she'd probably do ok and quite a number of her friends have been before. Then maybe a separate gift for the 1yo (and who can guess what they'll latch onto at that age, LOL! Everything and nothing...)

One combined gift that has been great for my kids was the addition of a sand/water table. Both of them at 3 and 1 enjoyed it (the sand got too messy for me so I just made it a water table) and during summer they happily played together for ages with it!

Otherwise, I second the art supplies, or Gelli Baff & bath crayons & bath toys. (Bath toys are always a goer IMO because they get so grungy after a while if you don't keep up with keeping them super clean so I am always chucking stuff out.)