A couple of questions:
- Will you have a dinghy?
- How many nights will you be out?
I think Bubblehead covered West River pretty well. I'll add that if you have a dinghy, you can anchor (for free) in the roadstead beyond the moorings in Galesville. (You can even tie up to the community dock, temporarily (&free) if your draft isn't too deep.)
There used to be a real nice old country general store in Galesville, where you could get breakfast/lunch/provisions/ice cream. But unfortunately, it closed down a number of years ago. The restaurants BH mentioned will be your best bet for ice cream.
I also like BH's recommendation for Rhode River. It's a good spot for kids if you have a dinghy and can take them ashore to some of the little islands. No place to get ice cream, though. And the motorboat traffic on weekends can be a bit tedious.
Nick's suggestion of St. Michael's is a great one, but reading your post it sounds like you may have only one night? If so, St. M's is a bit of a stretch since you will spend much of your time in transit coming and going. Kids and moms usually like a fair bit of down time for swimming/exploring ashore and playing/lounging around on the stationary boat. St. M's might be too ambitious.
I might offer one other idea: How about daysailing out of Annapolis, then returning to snag a mooring and taking the water taxi ashore for ice cream? Spend a very comfortable night securely moored in the harbor, then out for another daysail on Sunday. Maybe head up and under the Bay Bridge as a destination/objective -- the kids will love it. Or if it happens to blow like stink, you have the option of going up the Severn.
Yes, not as adventurous. But, if this is one of your few outings with the kids and mom aboard a sailboat, the key is little or no drama/stress so everyone will want to come back for a longer charter next time.
Okay, I'm rambling here, but I have one other suggestion: If you want to get out of Annapolis, you could come out the Severn, hook around Thomas Point Light (always fun to sail past with kids), head up the South River a bit and then duck into Harness Creek. There is a really nice park there ("Quiet Waters"), where kids can go ashore and walk the trails. There is also a little boat rental shop that rents kayaks, pedalboats, etc, and even has ice cream and popsicles. You can anchor just off their dock (leave a minimum of several boatlengths to avoid crowding them). It's a good spot for kids, in my opinion, and a well protected anchorage.
Have fun, whatever you do!