Glad to see that you've been able to salvage your cukes and summer squash!
However, these are both fast growers and showers, and are best started right out in the garden. For most cucumber and summer squash varieties, you're looking at 50-70 days for production, which is well within the range of a "summer" season, even in the coolest contiguous US climes. If you want to start them indoors to get a "jump" on a short summer (I don't recommend this since they don't take to transplanting well), you shouldn't start them more than 2 weeks before your typical last frost, use peat pots, and plant them out as soon as all risk of frost has passed. I know I'm a lot warmer than you down here in DC, but I can actually do two full rounds of both cucumbers and summer squash (plants grow, produce, die out, and are replaced) from seed in the garden, no starting indoors, so you can absolutely get a good crop just plopping the seeds in the garden once all risk of frost has passed!
