Just a couple of ideas...
Our DS got Mega Bloks for his 1yr b-day; sometimes puts 2 or 3 together, but also enjoys taking them apart (after we put them together) and enjoys putting them in & out of the clear plastic zipper bag they came in. Maybe the boy could build, and the girl deconstruct.
Also, a good outdoor/warm weather toy is a water table or a combo water/sand table. If we had the space, we'd definitely have one. For the ages/development stages... maybe get one with accessories (water wheel, or water/sand toys). The girl, who's just now cruising, might enjoy just standing at the table & splashing, while the boy could pour, etc.
I'm sure there are plenty of other good ideas, just can't think of them at the moment.