We need a voltage transformer that will be able to handle 3 american sewing machines and 2 computers. Madagascar runs at 220v, but the power is often inconsistent and there are significant surges. I would like to use a step up/down transformer (220v to 120v) in combination with a Tripp Lite surge protector. Is that redundant? Can I also use a power strip with the transformer, or is that a bad idea?

Thanks.

Why not consider a UPS (Uninterruptible Power Supply) which will provide you with the 120 volts you need and also provide filtering and surge suppression.