Peas are safe to put out as are salad crops - tho if you sow direct they will be a bit slow (mine are!) I tend to start most veg crops off inside on the windowsills (I don't have a green house- but have one on order!) and then acclimatise crops in the coldframe or outside during the day before planting out.
Hope you enjoy growing veg- I started 5 yrs ago and am now fully converted.PS - the best tip I was ever given was only grow what you like to eat- there's nothing worse than having a crop you looked forward to fail and a novelty crop that you grew just to see if you could, thriving, leaving you overwhelmed with mountains of something you don't like. (I had massive bags of radishes and courgettes my first year)