Oops, got carried away with your Brug question and forgot to continue with the fruit trees - Are you bringing them into the house in winter also? The mango, at least, will not do well with any frost at all. Not sure about the lemon as some varieties are hardy = they will "survive" but not necessarily thrive.
A tree started from a seed will take years to bloom and fruit, especially a mango - mine took 3 years and I started with a 3-yr old baby tree. The lemon, it kind of depends upon what variety it is. Was it a grocery store lemon that you got the seed from?
It also depends a lot on the weather - if we continue to have a run of warm-ish winters your plants may come along to blooming/fruiting size a little faster.
Another consideration with the mango is, they tend to want to bloom in the winter and early spring here, and you definitely will not have any pollinators for it if it's inside your house, so this further reduces your chance of getting fruit. Oh, and the flowers smell terrible (at least I think they do).
In summary, I'd say keep the lemon as they can make nice, pretty house plants that you can keep pruned down to size, and have beautiful fragrant flowers. The mango really isn't going to make a good indoor plant - it will very quickly be too big, probably make stinky flowers at the wrong time of year and most likely will never give you fruit.
