I've thought about it, but haven't done it yet. The probable reasons I haven't had one are that I work from my home and our client-friendly entertaining area might be a bit small. Plus I'm not sure how comfortable my clients would feel meeting each other, or even the thought of meeting other clients. Plus, we're pretty low-volume, so it's not like we have a couple hundred people to invite, and we're afraid only a fraction of what we do have would show up! LOL
But things you could do if you were considering one, would be to have healthy snacks, give little 5-min chair massage freebies, announce/debut a new product or service you plan to offer (along with demonstrations, if it's feasible and if you want to), hand out new newsletters, give a small presentation on health-related issues that complement (but aren't related to) massage, announce a networking partnership with other healthcare professionals, etc. Kick off a referral race to grow your practice. You could give door prizes too (for most frequent client, most improved case, or the most referrals or whatnot). Whatever.
The possibilities are endless. It could be a blast for both you and your clients, and you could also refresh, renew, or jumpstart your business.
Just make sure you have plenty of space for your clients, comfy chairs for them to sit, enough (but not too much) food/drinks if you plan to offer them, and keep it lively. Also, I wouldn't do it all day or anything. Maybe an hour or two. If you have a large clientele, you could run it all day, and have people come and go as they like. However you like to run it
Just my rambling ideas
Hugs,
~Jyoti