Workathomehe11, hello and welcome to our little corner of the net. I gather from your request that you have no broadband internet to your house. If you did, your son could use that and also it might be possible for you to logon to work, with a secure VPN connection, and you would have more speed.
Alltel is a cellular provider, so this Data Card is probably a cellular modem. A cellular modem is not really designed to be shared, you are supposed to get a card for each system that connects. I see from Alltel's website that they have speeds "up to" 3.1 Mbps, which is not bad if it really does that speed. Of course, the whole "up to" clause means it can run much slower. Usually people use a cellular modem because they are on the road a lot -- either traveling out of state or just around the city. But it sounds like you are working at home and your son would be connecting from home, too, so a cellular modem might not be the optimal connection for you.
If you are in range of a cell tower, you are not in some remote area so you could almost certainly get DSL or cable modem broadband to the house for less money than a cellular network plan and with more bandwidth. Then a router would allow all of the systems in your house to connect through the same broadband connection, wired or wireless. You could switch your wireless plan to Alltel hotspots instead of Internet anywhere so you would still have the option to connect away from home, but only at a hotspot and not just anywhere.