I'm going to answer both questions. About the toys on the shelf. You can switch the toys around whenever you feel like it, depending on Irina's cues. Every 2-3 months it's nice to sweep some newness into the playroom by exchanging things that perhaps she hasn't showed much of an interest in. as long as she has some of her favorites in there and nothing electronic, battery operated or too distracting, trust yourself!
With meal times. We tend to encourage our children to have meals in the playroom because of the element of control we want to give our children. In the playroom, we don't have as many time constraints as to how long it should take to eat a meal. It doesn't matter too much if she makes a mess because we design the playroom for easy clean up. There are also not as many distractions for her to contend with (e.g. your own plate of food, focusing on your own meal, etc).
If she makes a mess, one suggestion is to keep the plate on the shelf and bring spoonfuls or forkfulls of food down one by one. If she wants the whole plate, then it's a matter of being easy and relaxed (even if she makes a mess) and allowing some time for clean up once the foods gone. Letting go the idea of her having to use a spoon, clean her hands and face, etc until the meail is over. You could use some explanations to help make it more manageable (e.g. "we usually don't throw our food but eat it instead", or "I will keep the food on the shelf and bring it to you so that we can keep our playroom tidy", etc).