Hi Tanya
And welcome to the forum
I wouldn't worry about your Yorkie puppie playing with your Spaniel. We got our Yorkie Zena when she was 8 months old and she was playing with the neighbours collies' straight away and an 1 hour long walks were no problem at that time. If you get a young puppy, just keep an eye on them while they're playing
But hopefully someone else has more advice about the very young ones
Anyway, I hope you enjoy the forum!
Take care,
Karin