Last weekend I took my family (including two kids) on an day trip to the Wachau to see the tree blossoms. We had done two similar trips last year. This is truly a lovely time of year to visit this area as it is full of apricot, plum, apple and cherry trees. The blooms had not yet hit their peak when we visited, but that made the trip no less lovely.
Based on my trips last year, I found that the best place for tree blooms is the area around Rossatz/St. Lorenz, which is opposite of Weissenkirchen and Durnstein. I had found a good resource online for this area with mapped paths:
http://www.marillenmeile.at/index.php?id=9
Looking at the map at the bottom of this site, we took the "blue" route this year (and the "red" route last year). Both were equally lovely. The paths are a mix of foot and bicycle paths (no cars) and right through the vineyards and orchards, often along the river. The "red" route has beautiful views of Durnstein.
So to get out there from Vienna, you make your way to Heiligenstadt, the end station of the U4 line. Walk over to the train platform and get on the train to Krems (1 hour). From Krems, take the WL2 bus (not really a bus, more like a big minivan) and exit at Rossatz for the red path or Ruhrsdorf for the blue path. The bus takes about 20 minutes from Krems. Check www.oebb.at for all schedules.
So last week, we exited the bus at Ruhrsdorf. There is a great little place to stop for lunch directly opposite the bus stop (they were serving rhubarb strudel last weekend!). Then walk towards the village and you'll hit the path. We took the path towards Rossatz and then looped back to Ruhrsdorf. We continued on to St. Lorenz where we then took the ferry across to Weissenkirchen. This is a car ferry and it costs 2 Euro per adult on foot. It goes back and forth a couple of times an hour (we waited about 20 minutes).
Once in Weissenkirchen, we wandered the town (had been here before, but had forgotten how lovely it is - I think I prefer it to Durnstein as it is less overrun). The church is worth a peak and you can walk along the old ramparts. We were hungry, so we found our way to Weingut Mang Hermenegild, which is on the main road by the river. Absolutely lovely, large garden with a playground and outdoor seating. Wine was good and food was cold cuts and cheese. Highly recommended for families.
http://www.weingut-hermenegild-mang.at
We then got on the WL1 bus to Krems (once an hour; 20 minute ride) and got on the train back to Vienna (Heiligenstadt, end station is Franz-Josefs Bahnhof).