We're having a little 10 wk old visitor

[Marsha]

We're going to dog sit for a friend next Friday. The puppy is a 9 week old Yorkie. He must not weigh 3 lbs.!! He's tiny!! Spanky is about 25 lbs., just turned 1 year old, and he's quite playful and puppyish. They met each other at our house today. There was no aggression on Spanky's part. His tail was wagging, and he was quite excited. He was jumping on us to try to get a sniff of Curly, the puppy. That scared Curly. However, Curly did eventually want to get down on the floor. He didn't seem scared at all about Spanky, then, but we were restraining Spanky for the most part. Spanky wanted to rush up to Curly and sniff, but, in the process would step on Curly. I followed Curly's mom's lead, and she was afraid Curly would get hurt and didn't want them together without Spanky being held. Spanky is a small dog....25 lbs., shorter than a Beagle, he's a terrier mix, but the size difference is huge. Spanky is still quite puppy-acting, though, and this puppy hasn't gotten adjusted to his new home yet, let alone ours. He is very tentative still....they've only had him 5 days. I'm guessing that next Friday, I should keep the 2 of them separated at all times. Is that right? And I was also wondering how you would introduce them if they were going to live together (they're not). We had kicked around the idea of getting this puppy's brother. We've already decided not to, but could it work out with Spanky being such a puppy still but so much larger than a small-breed young puppy?

All that to find out if it's best to keep them separated this time and anytime Curly's over until he grows a little, and 2, if it's possible to have 2 pups with these age differences come together without the little one getting hurt?
I hope this makes sense. I fill like I'm rambling.