I don't think so. I wouldn't let my tiny dog "play" with a 100 lb. dog any more than I would let a big dog "play" with a horse. I am not saying they have to be totally separated at all times but when one paw (or hoof) is kicked in the wrong directions someone's going to get hurt.
It's no different than a 100 lb. person stepping on a tiny dog. Or a grown man wrestling with a toddler. Keep your babies safe!
This is not directed at families that include "children" of all sizes. You know your dogs and your dogs know each other.
I hate to hear anyone sound pressured when they feel uncomfortable about something. If it doesn't feel right, play it safe.