Personally I wouldn't bother if growing in raised beds. I turned my whole allotment over to raised bed production four years ago. It's a side effect I hadn't expected but I haven't any slug or snail damage since.
The other solution, which brings many benefits, is to raise crops which can be transplanted in pots before planting out. For example I grow my brassicas in 10-13cm pots until they're around 20cm tall. Plant these out with the first true leaf at soil level to give well established strong plants from the word go.
The larger the plant you can put in your beds the faster they will establish and will be less susceptible to pest attack during this time.
Definitely raise transplants if you have facilities..
I probs raise 80% of my cropping that way.
Or buy them in if you don't have capacity to look after them
Although it might be harder to source bought in plants this year, I know a few nurseries have packed up for now, but I guess online sales will soar.
Transplanting, also gives a chance to get the ground weed free. But they don't want to be too big when you transplant, or it will stress them.
Re the raised beds / mollusc issue I'd sound a slight note of caution though.
Depends on the soil type, and what is used to edge the beds.
Slugs and snails will enjoy the crevice btxt soil, and edging material. to hide in in the daytime.
It's worth going out with a head torch and a pair of scissors, to catch em at it, at night .
And if the soil is very light and sandy then raised beds will dry out quickly.
I'd agree re plastic greenhouse, they are wind prone, and to extremes of temperature, because of their relatively small size.
I've seen far more abandoned / repurposed ones, than any being put to their intended use - although if you're there all day to babysit it, it could work out better.