Try to relax and enjoy. Probably first of many future times. Is it going to be in your home, or theirs? Easier for baby if she is in her own home, but as you mention sleeping in travel cot, sounds more likely it is going to be in your home. Just a warning, whereas baby is likely to settle down and sleep normally, do not expect for yourselves to have a good night sleep. As you will be on edge and anxious the whole night.
I brought up seven children, fostered nearly forty babies and toddlers, yet the first time I had a g.child with me overnight was a nightmare for me. More anxious than any first-time Mum!!! She was in travel cot in room next door to mine (both doors left open), yet about every hour during the night I went in there to check on her (think she was about six months old at the time - and was used to me and my house, as I looked after her two days each week).
I needed to check she was breathing, stroking her cheek to get a reaction. Totally daft!!!
Of course, she survived (in the middle of GCSE exams at present). And I survived also.