I been to Mont Blanc and the Zugspitze, but not to the other three, so I'll only answer for the first two.
PricesGuided ascents of Mont Blanc, including instruction, start just above 1000 EUR pp. Gear rental is a small amount compared to that. Without experience, going without a guide would be stupid, but, obviously, it will be much cheaper. Taking into account cable car fares and a night or two in the refuge, you're spending between 100 and 200 EUR. And there are still cheaper ways.
If you can read a map, then you don't need a guide for the Zugspitze via the Reintal route. The first day you can hike up to the Knorhütte. Sleep there, go to the summit the next day. Descend the same way and either spend another night in the Knorrhütte, or lower down in the Reintalangerhütte. Some might suggest hiking back down all the way, but planning to do that with a group of 8 with no experience that would be a very bad idea. In general, for a night in an alpine hut, count on 60 EUR pp, including dinner and breakfast. Perhaps a little bit more.
SuitabilityWhile inexperienced people book guided ascents of Mont Blanc, and quite a few actually make it, I would not recommend this, certainly not for such a big group. Most people hiring a guide actually have some experience already.
Try easier, less committing and less dangerous mountains first, and if that goes well, you can come back for it later. Or gain much more experience and climb it without a guide.
The Zugspitze is fine for beginners. And in case some of you are less fit than you think and are too tired on the summit, there is a cable car that can take you down quickly.
Finding guidesAs I wrote earlier, I do not recommend Mont Blanc, but if you still want to go, now or after getting some experience, then check out the
Office de Haute Montagne. Alternatively, you can try to get personal recommendations for local guides by people you know. If you are a member of the
Nederlandse Klim- en Bergsportvereniging, you can ask them to help you with arranging guides for your group as well. With a group of eight, you can have a custom made trip.
Other MountainsCountless! But it all depends on what your group really wants. Do you want a simple walk up? Glacier travel or not? Some scrambling or not? Or more technical rock climbing even? How many days? How do you feel about cold temperatures? And thin air?
Not knowing your group and your wishes, I couldn't even begin to suggest more mountains.
Good Luck, Rob