dont get an adult. they cost too much especially if you get a female (i have seen them for £80+). males cost less because they will be dead in a few years of purchase.
get a juvenile and you can watch it grow and the initial costs will be lower. feeding is really cheap, and rather than crickets or locusts i use meal worms for the young ones and morio worms for adults, barely any chance of escape and much easier to feed with.
i would say buy one of these: http://www.thespidershop.co.uk/insect/product_info.php?products_id=2300
not a smithi but in my opinion a better looking tarantula. i bought one a fewweeks ago and its a good size, not so small you have to feed it really small stuff, but its also brightly colored.
all you need for the set up is a cocofibre brick. a medium tank (i would say about 25cm x 20cm x20cm if not a bit smaller), the best ones being the acrylic tanks with the ventilated plastic lids which clip on really tight. and a few bits of decour and a hide (smash up a coconut and put the bits of shell in).
and do not pick it up.
as for your dad, i hated spiders, even when i first kept scorpions, so at an invertebrate show i bought the biggest female Chilean rose (grammostola rosea) i could find and basically im now only a bit wary of venomous things that aren't in cages. tell him to stop being so afraid of it and then when your mother sees how he got over his (rational) fear of spiders, she will look really silly if she is scared of a gecko.