I have a 7 month yorkie, Twinkie (my first tiny), who is 2# 4oz and she was much easier than my other 2 dogs who are both chihuahuas and 4.5#'s and 5#'s. Twinkie was not wee wee pad trained when I got her at 5.5 months old, but within 2 weeks she was completely potty trained. This was fast compared to my male chihuahua who I got when he was 12 weeks but was not fully potty trained until about 7 months.
As for playing, Twinkie will play with them with no problem. I was really worried when I first got her that she would get hurt but she beats up on my 2 chihuahus so I no longer worry about her. I would keep an eye on your little yorkie until you're comfortable with the 2 playing together.
All 3 dogs have an ability to get underfoot, but they learn quickly to keep out of the way
