Is your driveway all in shade. Hostas are shade plants and they come in all heights and leaf sizes.

I have never heard of hostas grown from seed. They are very easy to divide and grow so fast that even if you could buy seed I don't think there would be much call for it. Now horticulturists must get seed because they are always coming up with new varieties. I would think it would take a long time to grow to a usable plant.

Check out the sellers on line. Often they have hosta deals. I wouldn't try to do the whole thing at once. Space them apart and add a few annuals for the first few years. Then every year or 2 you can divide and fill in with hostas

I would hedge my bets. I would space out some mature plants, drop some bulbs into the ground in between, then plant some annuals circling the bulbs. Between natural spread and bulbs growing in you'll have a dynamic situation to enjoy watching develop.

Hostas are easy to grow from seed and don't need cold stratification. I'm growing them from seed I harvested from my own plants a few years ago. They take a really long time to get any size to them. The ones I planted 6/20 last year went dormant in December but are back up again this year. They still only have about 3 leaves on them. They won't come true from seed--the ones I'm growing all came up green, even the seeds from variegated cultivars.
Oilpainter is right--it's faster to divide mature plants every couple of years to increase the number of plants you have to work with. You can also divide them into smaller segments. I've got smaller divisions planted around the base of an oak tree. They'll be small this year but slightly bigger next year. By the third year they should have grown to almost their mature size. I've got some gigundo designer hostas that need to be divided but I missed my window of opportunity this year.
I also winter sowed hosta seeds. They're tiny but they're up. Check out www.hostalibrary.org for instructions on how to grow them from seeds. I grew them indoors last summer by a sunny window. This year I winter sowed 2 different types of seeds--'Dream Weaver' & 'El Nino.'

Many people grow hosta from seed trying to see what variations in plants they can come up with...they don't come true to the parent plant. Takes some patience....germination may be anywhere from 15-90 days or so, and the plants stay small for the first 2-3 years.

Hostas are not bulbs. They have a root system extending downward from a crown, and quite an extensive one at that...One of the few times I've broken a shovel was lifting hosta to divide.