Does anyone know a private car service that can drive us from Venice to Monte Carlo
I assume you mean Monaco and not Montecarlo which is fairly close to Venice. That is about 350 miles and 6 hours so it might be hard to find someone willing to make that long a trip. But I would contact a local taxi service in Venice or the hotel and see if they have a recommendation.
Just thought it might be a nice way to travel, but I can't seem to find anything at a reasonable price. Thanks.
Sorry, can't help directly, but to agree with Frank, and even more. Not only is it 6 hours minimum to drive it plus rest stops but that driver has to then rest the legal time which is probably overnight before their 6 + hours drive back. So, in addition to their fee you would also be on the hook for probably 2 days' food as well as tolls both ways and their hotel overnight. I bet it wouldn't be much more to charter a jet to Nice and take the helicopter to the Monaco helipad next to the Princess Grace rose garden.
Check out the train. You have to make a couple of changes (it's not direct), but it looks like a little of 6 hour trip. It's $93 per person on raileurope.com
Use something other than Rail Europe for pricing and scheduling. RE is too limited and tends to overprice.
Rail Europe is not your cheapest source for tickets. Besides paying higher fares, you will have to pay an $18.00 delivery fee. The standard 2nd class fare for Venice-Milan on a high-speed EuroStar Italia train plus Milan-Ventimiglia on an IC train is €59.00. That's $77.50 at today's exchange rate. The fare for Ventimiglia-Monaco on a regional train is €4.00 ($5.25). If you book well in advance (up to 120 days allowed) at trenitalia. com, you can get a Mini fare as low as €9.00 for Venice-Milan and a Mini fare as low as €9.00 for Milan-Ventimiglia. With the €4.00 you will pay for Ventimiglia-Monaco, the whole trip could cost you as little as €22.00.