XC skis will have a wide range of widths depending upon exactly what kind of skiing they're targeted to, but most starter kids' skis will be targeted to in-track use and fairly narrow. A very rough guide is that this type of ski will be about as tall as you. I'm guessing that those 110s will be pretty small for a 9 year old...I think that my XC novice 9 year old is using 140cm waxless skis. Skate skis will remain thin and be somewhat shorter...out of track/backcountry skis will tend to be wide and long to get some real float.
There are two major "modern" binding types, SNS (single wide block on binding) and NNN (two thin blades on binding). You really have to just look at what is on there and get boots to match. There are also backcountry (BC) versions of both bindings, but I would think that you wouldn't run into those in stuff for kids. I'm not even going to get into skate bindings...
XC boots will usually use Euro sizes...my daughter wears a youth size 3 shoe and just stepped up to size 35 XC boots. I wear a men's 12.5-13 shoe and 47 XC boots.
If you have an LL Bean store around you, they can be great places to troll for cheap XC boots for kids...last year, we got boots for $5 (basic Karhus). They had dozens of pairs, and we should have bought several in ascending sizes for her so she'd have been set for years...hindsight is 20/20.
Hope this helps!