Truffles are a bit more of a thinking type trip, expands the mind a good bit but cleaner (depending on dose, milder) visuals. Was in the Dam this past summer, and I can say that they're not as easy to come by as they were 8 years ago, as the laws are tightening up, but they're still available. They're not available through the coffeeshops, so go to any "smartshop" and ask discreetly and you'll be able to find some.
They're about the consitency of macadamia nuts, with a milder taste than cubensis... at least the ones I tried were. Any type of "sclerotia" will be what you're looking for. Tried mine in 2001, and they were in fact labeled as 'Philosopher's Stones' but I'm not sure of the specific variety. There are a few different types. They sell em in pre-measured packs over there, not really in different size doses. The guys at the shop will help you pick which type based on the effect you're looking for, so ask about that when buying and they'll dial you in.
The cubes I ate over there were the BOMB compared to all the dried ones I've eaten here, but no better than freshies here in the states. If you've never eaten fresh ones I'd stay away from those if you're not looking to trip too hard around family. They'll be about 35 grams in a pack which equals about an eighth dry weight. So for cubes, you'd want about 15 grams fresh weight to equal 1.5g dry weight.
Don't really remember the weight on the packs of sclerotia, but what I'd recomend is taking about 1/3 of the pack to start and see how you react, especially if you're hanging out with Pops. Can always take a bit more if it's not as strong as you're looking for but if you eat too much to start, all you can do is wait it out with a lot of paranoia from being too fucked up... Give em about 45 minutes to kick in before you eat more. They'll work faster and harder on an empty stomach, so keep that in mind as well. I like to eat a small sandwich or something an hour or so before I trip so I'm not totally hungry during.
Last recomendation, out of my 13 trips to Amsterdam, my absolute FAVORITE activity while tripping was going to the Heinneken Experience! Very interactive tour through the museum, including a few semi-amusement type 'rides'. Lady knew we were TRIBBIN BALLS and let us right on through

Also, got 3 beers and a souvenier glass at the end. Can't beat that with a stick man!
Good luck, and remember, can always sleep when you get home! Have a blast!