I am also quite small and only have two rooms. I usually greet guests and provide a treat from our kitchen. If I know I will not be available all afternoon, I will normally send an email through Booking.com to ask them to let me know what time they may be arriving, so I can ensure that I am onsite to greet them. I then provide them with directions on how they can enter their accommodation. We have pin codes not he door so they can enter without keys which makes it so much easier. I will normally text guests the morning they are due to arrive to ask their expected time of arrival. Overseas guests, I need to rely on Booking.com email system and hope they check it prior to arriving. Generally these methods work. We live onsite and don't have a front desk, so I will send instructions if I know there is a chance that I will not be here at their expected arrival time.