A script that you can wrap with helper scripts to make it easier for your kids to start up the Minecraft server on their own.

gce_server.py

#!/usr/bin/env python

# sudo pip install --upgrade google-api-python-client

from apiclient.discovery import build
from oauth2client import client, GOOGLE_TOKEN_URI
import argparse
import httplib2
import sys

CMD_URL_TEMPLATE = "https://www.googleapis.com/compute/v1/projects/%s/zones/%s/instances/%s/%s"

parser = argparse.ArgumentParser(description=
"Starts/stops a Google Compute Engine instance using an OAuth refresh token.\n\nExample: gce_server --client_id 12345-abcdefg.apps.googleusercontent.com --client_secret abcdefg-x --refresh_token 9/aBcDeFg --project my-project-999 --zone us-central1-a --instance game-server-1 start")
parser.add_argument('--client_id',
                    help='Google API Client ID (https://console.developers.google.com/apis/credentials)')
parser.add_argument('--client_secret',
                    help='Google API Client secret')
parser.add_argument('--refresh_token',
                    help='Refresh token for obtaining access token')
parser.add_argument("verb", default="start",
                    help="Either 'start' or 'stop'")
parser.add_argument("--project",
                    help='Name of the GCE project that contains the instance')
parser.add_argument("--zone",
                    help='Name of the GCE zone where the instance is')
parser.add_argument("--instance",
                    help='Name of the GCE instance')
args = parser.parse_args()

credentials = client.OAuth2Credentials(
    access_token = None,
    client_id = args.client_id,
    client_secret = args.client_secret,
    refresh_token = args.refresh_token,
    token_expiry = None,
    token_uri = GOOGLE_TOKEN_URI,
    user_agent = None,
    revoke_uri= None)
http = credentials.authorize(httplib2.Http())
credentials.refresh(httplib2.Http())

h = httplib2.Http()
headers = { "Authorization" : \
            "Bearer %s" % credentials.token_response['access_token'] }
url = CMD_URL_TEMPLATE % (args.project, args.zone, args.instance, args.verb)
(resp, content) = h.request(url, "POST", headers=headers)
if resp.status == 200:
    print "Success. Action '%s' should be ready soon." % args.verb
else:
    print "Something is wrong. Email this to Tech Support:\n\n"
    print resp, content