Invite who you want to invite. even if you like their foofriend, sometimes you just want to hang out with a friend, and not compete with foofriends to get quality time. If they want to bring along the foofriend, they can ask if it's ok. Sometimes it's not and you shouldn't be afraid to say so.

I know it used to depress me at how my other single friends fell off the planet once they started dating. I tend to plan more group social events when I'm dating, to make sure I still see everyone. Although, I don't know if it's really possible to plan more events than I have been in the past year.

Then again, I usually avoid dating established friends out of fear of hurting the friendship (which I need more than the big R relationship). Hence, I'm usually in a situation where my date is not always emotionally reassuring, or doesn't have enough common interests, and I need my friends around to recover from that, to remind myself I have a life beyond my date.

I'm in the weird (but much more emotionally satisfying) situation of dating a friend now. We have tons of common interests and friends, so we already do a lot of group stuff with each other. When events come up that I would've invited several people to, it's a tough call. It's an opportunity for an exclusive date, but I sometimes feel like I'm blowing off my other friends by not inviting them.