Try it first in the "Dutch Alps" ;o)
Actually you should be fine.
But if you are a belt-and-suspenders type personality like me or expect strong wind-driven rain you can:
Re-coat the silnylon tent with a 5:1 ratio by volume of 5 parts of odorless mineral spirits to 1 part clear GE Silicone II (or European equivalent). Place in a suitably sized jar with a tight lid. Shake well to mix and shake every 5 minutes while using.
Apply in sections with a very short nap, narrow paint roller – pour small amounts in a roller pan. You can also use a fine bristle brush. Spreading the tent sections on a smooth top table is far better than using the floor.
BE SURE to wipe the excess off each section immediately with a heavy duty paper towel ("shop towel"). Rolling on the mix is faster and gives a more even coat than brushing. Wiping immediately after leaves only the necessary amount on the silnylon, thus reducing weight AND GREATLY REDUCES DRYING TIME by days. Silnylon floors or ground cloths ("footprints") can be coated twice using this method for a heavier coating.
BTW, this procedure will seal the tent exterior seams but I would recommend also coating the interior seams as well. If seams ever leak after this treatment (doubtful) use a 3:1 ratio of mineral spirits to clear silicone caulk for re-sealing. Do NOT wipe this seam seal treatment. Just let it dry in the hot sun. The Netherlands does have hot days, right? My experience with Dutch weather was in late October when it was cold and rainy.