Biking with young kids- tips?

Any tips on biking with young kids? We'll be biking daily in the Netherlands in June with our kids, ages 2 and 4. The 2 yr old in a bike seat the 4 year old on a slip-streamer. Any tips from those who've done it on keeping the kids happy? They like the outdoors and we do a lot of hiking and skiing (with the younger child in a backpack) at home, but we don't live in a bike-friendly area so they haven't been much exposed to that except a bit during out short summers.

Thanks!

Global Family Adventures

There is a very good site on cycling with children, albeit it is in Dutch:
http://www.fietsenmetkinderen.com/</a>