First time growing petunias,nasturtiums and marigolds

[cjp1953]

This is the first time growing these.Marigolds are 2 inches high with 2 and 3 sets of leaves.Nasturtiums are around 4 inches tall and petunias are still small.The weather is going to be in the 50's and 60's later this week during the day.Right now I have them under my shop lights but I need the space for my tomato and some pepper plants I need to repot into larger cups.At what temperature can they go outside?I have a couple 20gal aquariums not being used I could use as a greenhouse.I could bring them inside my garage when the sun sets for warmth.Any tips will be appreciated.I hope to repot my tomato and pepper seedlings next week.