Defo go ahead with the 'Meridian' for cost and the ease of mounting an engine - it'll make a fine ride and a great first project! I jus' wanted ta offer a bit more to help a clearer picture of the topic in general, there's a great diversity in "trikes" and not all their quirks known is all
I'd not start a first project with a recumbent unless ya already had one, they're a bit odd & usually quite expensive.
BTW, "tadpole" just means a tricycle with two wheels in front, "recumbent" just means a more prone position then sitting bolt upright so there's no need to "convert", they can be bought that way just like an upright delta, like your 'Meridian'. A tadpole can also be upright, like fasteddy's Indian Tri-car project;
...which will look something like this, only shinier;
BTW, more info can be found in Silver's thread here if you wish;