From what I've read online, starting with single malt whiskey is probably a bad idea for a rookie because I probably won't like the peat or smokey taste, and would probably prefer a blended whiskey. Maybe something like Maker's Mark?
And from there, start with mixing it with water? And for my wife, I doubt she'd drink it with just water. Possible to do mixed drinks with whiskey?
"Single malt whisky" refers to whisky from a single distillery. Not all of it is smoky or peaty, in fact the majority isn't peated at all. All whisky is matured in oak barrels, usually ones that have already been used to mature bourbon or sherry, though many kinds have been used - virgin oak, port, various wine casks etc.
Bourbon-cask whiskies are the most common, due to the steady supply from the US, and can run the gamut in taste from extremely light and grassy, to citrus or tropical fruits and nuts, or strong toffee and caramel flavours. Sherry-matured whiskies are typically described in terms of candied fruit, dark chocolate, and Christmas cake.
It's also common these days to mix different batches of whisky from different types of barrels into one release. As long as all the whisky was distilled at one distillery it's still a single malt.
The most common peated whiskies are from Islay, such as Lagavulin, Laphroaig, Ardbeg and so on. Not all Islay whiskies are peated though, and not all peated whiskies are from Islay
Blended whiskies are typically softer due to the grain whisky that's used in them. Some like them, some don't, but it's definitely worth checking one or two out to see if you like the general flavour profile.
Makers Mark is a bourbon and would be completely different to anything in the Scotch whisky range.
Personally I'd start out with something that you think sounds good from online reviews. Sherry-matured whiskies like Aberlour or Dalmore are fruity and approachable for a beginner, or something light like the Glenlivet 12 already recommended. I really like the Glenfiddich 15 too. For a beginner Islay I'd suggest the Bowmore 15, I like it much more than the 12, but it sounds like you're not into that
I also wouldn't water it down right off the bat. You want to know how it actually tastes, right? Try it at bottle strength first (which with any of the above suggestions has already been watered down by the distillery to a standard strength, usually 40-46% ABV). Add literally a few drops of water at a time and keep tasting. Eventually you'll find the amount that you prefer. It will be different for every individual whisky so don't assume what works for one will work for another.
