They have toys, but, unless they are open-ended (LEGOS, for example), they won't give most toys their attention.
They are builders, too; a scrap wood pile, some hammer, and nails will keep them busy for weeks -- not just days.
They also love adventure; give them some non-functioning lawn tractor or even a steel barrel... well, you get the picture:
I already know that this summer will be a blast, if not also dirty and full of calls for band aids. How do your kids play in the great outdoors?