Should be able to Pammy - just watch the weather and, I assume, the plants are hardened off :-)

For the rhubarb, the leaves are poisonous, so birds are unlikely, but slugs are. If you want to eat the rhubarb, make sure the slug pellets aren't touching the ground, if the active ingredients include metaldehyde.

Re your tomato plants - keep an eye on the temperatures for the weekend, the last forecast I saw was for quite chilly. Just because its nearly the end of May doesn't mean we won't get any more frost for definite - we had a light frost in some places around dawn last night. If the temperature's above 6 deg. C as a minimum, they should be okay provided, as Moongrower mentions, they're already hardened off.

Ive got tumbling toms in hanging baskets and pots and mine have been out for a week now and are fine (so far) ....im in south wales.

You've taken a risk Cookygirl, as Bamboo says keep a watch on the weather forecasts.