yep they do indeed look smaller than the white ones, but I would say just as strong. In fact, of the very few pill reports about them, one states three were tested, with an average strength of 210mg (clean) mdma. Based therefore on how much I took and how hard I rolled/intensely euphoric I felt, I would have to agree with the strength this report claims. 
And so yes I agree, U shud defo start with a half (like I did/almost always do with strong dutch beans) and then maybe wait and see how u feel after u have peaked before considering re-dosing with another quarter or maybe another half. Note here, your first half will probably pack a pretty powerful but very pleasant punch (especially if it's been at least a month since u last rolled); thus even just another quarter a few hours later will no doubt have you rolling even harder in my opinion than the first half.
But I suppose the most important thing is the social setting which you say will be a good party and probably I guess there will be good friends present, so perhaps u won't want to get too mashed initially/at least for the early part of the evening/night in order to get the most out of this experience. Either way if you are rolling with others and stick to no more than one of these delushcious beans, I'm sure u will have a very memorable and wowee experience!!! 

I on the other hand only very rarely take as much as I did (i.e. 3 halves over a period of about 7 hours). I usually take no more than one strong dutch bean split into two halves or occasionally a half followed by 1 or 2 quarters) but I was rolling in my own home with a few very close friends having took a 2 and a half month break since my last roll (2-3 month breaks being my norm). Hence, I didn't mind getting more mashed than usual within this very safe/secure and positive environment. Finally, wud b great if u cud report bk here on ur experience with these beans once u've tried em. cheers :)